BugBlog

The window date of lace webbed spiders

2012-01-27T21:16:00.002Z

Last week I noticed a female Amaurobius similis, also called lace webbed spider, on the kitchen windowsill. After a few moments - enough for me to take her photo - she quickly retreated to a crack between the sill and the window frame (photo below). These spiders usually live in holes in walls, fences or windows, and have a characteristic fuzzy sticky white silk that radiates in strands away from the hole. Yesterday, late at night, I found the handsome male on the top photo, right next to the female burrow. It is not the first time I find wandering Amaurobius males in the house the first months of the year. Males and females mature in the autumn and males often come out of their burrows to find females. Once the male finds a female's burrow he will drum the threads with his legs and often vibrate his abdome too. They are fierce-looking spiders, with large, dark head and chelicerae, bright, orange legs with darker rings, and nicely patterned abdomen with lighter chevrons. Males have longer legs than females.

For more on Amaurobius spiders in BugBlog click here.

Buzzing laurustinus

2012-01-13T20:31:00.000Z

I planted a laurustinus (Viburnus tinus) bush on a large pot a couple of years ago and placed it opposite the window where we eat, a sheltered patio area. I did not realised at the time what a great location this was and what a fantastic bug magnet this bush is. One of the best features of lauristinus is its long winter flowering season (from October to May). My new vantage point has also revealed that their pollen and nectar rich flowers are often visited by honeybees, hoverflies and droneflies during mild winter days, as you can see in the photos below, all taken a few days ago. Come spring they are also visited by butterflies like the Holly Blue and early bumblebee Bombus pratorum queens. As this hardy bush does not mind shady conditions, their pink-white flowers are a good way of lightening dark corners of the garden.

A poor shot of Episyrphus balteatus

Eristalis sp. Dronefly.

The one on top of the post is possibly Meliscaeva auricollis, thank you Geoff F from WAB for the tentative ID given the difficult angle.

An early start for the butterfly year

2012-01-11T21:49:00.002Z

I just sent my record of the first butterfly of the year to the fantastic Woodland Trust site nature's calendar, a citizen science website which allow enthusiast naturalists to add their phenological data. It has fantastic live interactive maps and data is also used for scientific projects. Only once before I had my first butterfly of the year in January, but Sunday's (8th) was the earliest. A Peacock, flying strong, but coming close enough to us for ID (the photo above is from a few years back). We have had very mild weather since before Christmas, and this is stirring up hibernating bugs and bringing them out. All five butterflies, which spend the winter as adults (Brimstone, Small Tortoiseshell, Commas, Peacocks, and Red Admiral) had been reported in the Butterfly Conservation website by the 8th of January.

Christmas spider

2011-12-24T21:58:00.001Z

A large volume of search keywords hitting BugBlog are about spiders. "Scary spider" in particular features high on the search keyword ranking. I hope the blog helps dispel the myth of spiders as scary bugs. I thought fitting to finish 2011 with a not very scary spider, one that most of the time is hiding outside on the corner of windows, doors and railings in a little silky retreat, and that weaves a fresh web every morning all through the winter. Zygiella x-notata, the Missing sector spider, or window-frame spider, makes characteristic webs with a missing section, though which its signal threat runs (top left hand corner). This one's web glistened on the sun today, with the backdrop of cotoneaster berries that the blackbirds haven't quite finished yet.

Twelve bugs of Christmas

2011-12-22T19:48:00.004Z

Today we woke up to a mild, sunny day and I was pleasantly surprised by the diversity of active bugs about. I made a count of species and when I got to twelve I was reminded of the traditional carol and made up a buggy version:

12 ladybirds walking | 11 winter-gnats dancing |10 honeybees buzzing |9 bluebottles basking | 8 leafhoppers leaping | 7 woodlice hiding | 6 hoverflies flying | 5 snails sleeping | 4 spiders weaving | 3 harlequins | 2 drone flies | and a bumblebee on ivy

The honeybees in the local wildlife garden were coming out tripping over each other and ladybirds (7 spots mostly but also harlequins and 22 spots) were awaken by the mild temperature. I counted 5 spider species outside (Tegenaria, Zygiella, Pholcus, Steatoda, Linyphia). The main surprise was the bumblebee worker, extremely fast and active and with pollen baskets full with pollen.

Here is a slideshow of bugs seen and photographed today

Marsupial water slaters

2011-12-20T22:18:00.000Z

Water slaters or water-lice, Asellus aquaticus, scurry about the leaf litter of my indoor pond. They are fascinating pond inhabitants, always active, sometimes three individuals walking in a line across the tank walls. Most of the water slaters had broken antennae when I collected them, but they have now grown back, the new segments were still thin and transparent a few weeks ago (above), but have now fully developed. Unlike insects, which have very limited regeneration abilities, crustaceans can regenerate lost or broken appendages - as even when adults they carry on molting, and in each molt, they regenerate a bit more of the missing leg or antenna.

Water slaters tolerate a wide range of ecological conditions and are distributed across much of temperate Europe, Russia and North America. They are often abundant in polluted water and live in lakes, rivers, springs and even caves - where albino subspecies with smaller eyes have evolved. Being scavengers, they just need some detritus and fallen leaves and organic material to subsist.

In the last few days, a female has laid eggs into her brood pouch or marsupium. While she climbed over the leaves beside the tank wall, I took a photo where her yellow eggs are visible through the transparent brood pouch.

The marsupium is made of overlapping flat blades coming out of the female's anterior four pair of legs, and allows the mother to hold the brood under her body. This structure is a common feature of all Isopods - which include also terrestrial woodlice. The female not only carries the eggs but also the developing larvae. The larvae will emerge as miniature versions of the adults (see the figure below).

Fig. I. Marsupial stages of Asellus aquaticus. Top plate: A, stage A showing two membranes (arrows). B, stage B showing one membrane (arrow) and cleft yolk mass. C, stage B shedding membrane to reveal lateral outgrowth (arrow). D. stage C with its comma shape surrounded by a membrane (arrow). Bottom plate: A, stage C shedding membrane (arrow) to reveal stage D with free appendages. B, stage D with lateral outgrowth (arrow) and appendages covered i n a closely-fitting membrane. C, stage E showing setose body and appendages (arrows). It is at this stage that the juvenile leaves the marsupium to become free-living (from Holdich & Tolba 1981)

Occasionally females expel some larvae from the pouch - possibly due to physical limitations of how many she can carry as they grow - and larvae can also develop normally outside the marsupium from developmental stage B. Probably they need the ventilation and extra oxygen produced by the mother in the initial stage. Carrying the eggs and larvae is also bound to offer them some protection from predators, so it probably evolved as a form of maternal care.

Although water slaters normally stop reproducing during the coldest months of the year, my indoor pond is warmer than outside, and this might have triggered the start of reproduction; a situation that also occurs in wild populations downstream thermal power stations where water is warm all year round.

More information

Vitagliano, G., Fano, E., Marchetti, E., Colangelo, M., & Vitagliano, E. (1991). Importance of longevity, growth, and diapause in the evolution of Asellus aquaticus Bolletino di zoologia, 58 (2), 113-117 DOI: 10.1080/11250009109355740

Holdich, D., & Tolba, M. (1981). The effect of temperature and water quality on the in vitro development and survival of Asellus aquaticus (Crustacea: Isopoda) eggs Hydrobiologia, 78 (3), 227-236 DOI: 10.1007/BF00008519

Sexual roles and gender conflict in pond snails

2011-12-19T20:30:00.000Z

I caught these pond snails mating in my indoor tank today. The bluish, tongue-like structure between both snails is the penis of the snail on the background, entering the other snail's mantle cavity. So, that snails is acting as a male, (the one with a walrus-like head resting on its partner's shell) and the other as a female. Pond snails are simultaneous hermaphrodites, all individuals have functional ovaries and testis. The snails can self-fertilise, but if sperm from other individual is present, they prefer to use it. Although reciprocal sperm exchange might appear as a logical reproductive strategy, each individual snail might benefit more from acting as a male or as a female in a particular encounter with a potential partner. For example, large snails are able to invest in energetically demanding eggs, and might prefer to act as a female. Individuals acting as females are limited in the frequency at which they produce eggs, so they might prefer not to mate as often. Male reproductive efficiency might depend more on how many sexual encounters he has had, so snails preferring to be males might want to mate more often.

Sexual encounters of pond snails can result in just one of them acting as a male and the other like a female, or in subsequent reciprocation. But, the snails could disagree, what if both mating partner insist on providing, but not receive sperm? This is called gender conflict, and the resolution depends on one of the individuals compromising and adopting its less preferred role, at least initially.

Petra Hermann and collaborators studied the effect of age on sex role preferences in the great pond snails, Limnaea stagnalis, disentangling it from the effect of size. They reared three batches of snails that had known ages at the time of the experiments (young, Y, middle age M, and senior, S) and matched them by size.

First, they looked at the effect of age on mating interactions in age-matched couples. The chances of copulation decreased strongly with age, with young snails copulating with much higher frequency (80%) than senior snails (30%). Encounters between young snails normally ended in a reciprocal intromission (the individual acting as a female initially, then acting as a male), middle aged and senior snails, in contrast, had mostly unilateral sperm exchanges.

Then they set encounters between snails of different ages. When pairing young and middle aged snails, also size-matched, about 25% ended in no copulation, and unilateral encounters were more common than reciprocal. The primary role in the copulation (the snail acting as a male first) was adopted by the young snail in about 80% of the encounters, indicating that the male role is the coveted one for the young snail, and that the fact that reciprocation is rare indicates that the middle ages snail is content acting as a female in unilateral encounters. There is an age related shift in sexual role preferences from male to female.

Fig. 6. Sexual interactions between young and middle-aged Lymnaea.

(A) Most couples of a young and a middle-aged snail (YM) performed a

copulation. The majority of these interactions were unilateral, i.e. the snails

do not reverse roles after finishing the first copulation. Note that in the

cases in which the middle-aged animals acted as primary male all young

partners reciprocated. By contrast, role reversal occurred in only a small

minority (18%) in the couples in which the middle-aged animals acted as

female. (B) Younger snails act significantly more often as primary male than

their middle-aged partner. (modified from Hermann et al 2009)

They concluded:

Animals in the early phase of the species’ life cycle tend to assure that they act as male (either primary or secondary), independent of the age of their partner (Fig. 7A). Senior animals, by contrast, tend to act preferentially as females. The sexual behaviour of middle-aged animals depends on the age of their partner. Combined with similarly aged partners they either act as male or female. Combined with a younger partner they tend to act as female only. Combined with an older partner, they tend to execute both gender roles and will act as males with a similar probability as younger animals

Interestingly, the snails resolved conflict by engaging in reciprocation. When both agreed on a role the encounters tend to be unidirectional. Note that as these snails store sperm and the partners were not virgins, the lack of interest in copulation of the older snails might stem from the fact that they might have accumulated enough sperm to fertilise their eggs. So although the authors removed the confounding effect of age from their experiments, they failed to account for the effect of sperm storage.

The snails' efforts are resulting on these lovely egg masses appearing attached on the walls of the tank.

More information

Hermann PM, Genereux B, & Wildering WC (2009). Evidence for age-dependent mating strategies in the simultaneous hermaphrodite snail, Lymnaea stagnalis (L.). The Journal of experimental biology, 212 (19), 3164-73 PMID: 19749110

Pholcus phalangioides, the Daddy Long-leg spider

2011-12-18T21:11:00.002Z

In dark, forgotten corners of houses and outbuildings, a spindly-legged spider hangs upside down - motionless - from a loose, barely visible web made of very fine threads. It is Pholcus phalangioides, the Daddy Long-leg Spider or Cellar Spider. Today, several hang from underneath a wooden shelf in my outside toilet, including the male above. This species is cosmopolitan but has recently expanded its range northwards in the UK, and it is almost always found associated to buildings.

A male showing its palps.

Mating pair. After an initial male approach and web and leg tapping, if the female accepts him, the partners approach their ventral surfaces and the male inseminates the female using his palps.

Pholcus is a very generalist predator and has no trouble subduing large prey. I have seen it with captured Tegenaria (above) even Dysdera (below), the latter a spider with enormous chelicerae. Pholcus is able to do so thanks to its long legs, as it throws silk to its prey and wraps it on silk while keeping a safe distance. It can also invade other spiders' webs and then makes them vibrate simulating the effect of an entangled prey, in order to attract the owners and catch them, a deceptive behaviour known as aggressive mimicry. It will also eat other spider's eggs and trapped prey. If Pholcus is disturbed in its own web it has a defensive behaviour called whirling: it moves its body rapidly in a circle, becoming a blur, while keeping its legs on the web, this might deter other spiders from entering its web but even so, Pholcus can often capture and eat these spiders.

Pholcus is even able to capture and feed on woodlice, which often walk up the walls in my conservatory.

Female Pholcus are dedicated mothers. They hold their egg clutch of about 20 to 30 eggs by their chelicerae. The eggs in this clutch are close to hatching. The spiderlings' legs are visible through the egg shell as white threads.

The spiderlings stay close to their mother for some days after hatching. She hasn't fed since she laid the eggs and she will have to wait until the spiderlings disperse.

Pholcus go through five moults before maturity. The one below is molting.

Apparently, the most effective enemy of these spiders is that noisy generalist predator, the vacuum cleaner.

More information
Check this website for detailed information on Pholcidae.

Maciej Bartos (1998) Quantitative analyses of male courtship behaviour in Pholcus phalangioides
(Fuesslin, 1775) (Araneae, Pholcidae). In: P. A. Selden (ed.). Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997. 171-176. here.

Kazuyoshi Miyashita (1988a) Development of Pholcus Phalangioides (Fuesslin) (Araneae, Pholcidae) under Long and Short Photoperiods. Journal of Arachnology, 16 (1), pp. 126-129.

Kazuyoshi Miyashita (1988b) Egg Production in Pholcus Phalangioides (Fuesslin) (Araneae, Pholcidae) under a Constant Temperature and Photoperiod. Journal of Arachnology, 16 (1), 129-131.

Jackson, R., & Brassington, R. (1987). The biology of Pholcus phalangioides (Araneae, Pholcidae): predatory versatility, araneophagy and aggressive mimicry Journal of Zoology, 211 (2), 227-238 DOI: 10.1111/j.1469-7998.1987.tb01531.x

The CSI Blowfly

2011-12-11T22:03:00.000Z

At this time of the year, when there has been a few frosts and the sun is weak, the most likely insect you are likely to see on the wing are bluebottles. I found this one yesterday enjoying the sun in my conservatory. It is the urban blowfly, Calliphora vicina, a very cold tolerant species which is the most common buebottle in the UK.
Calliphora vicina is one of the most important species in forensic entomology, especially in investigating human remains. Different fly species arrive at a body at different stages of decomposition and they will lay their eggs on it. Blowflies can smell rotting flesh from large distances and are one of the earliest finding a body. They have a very fast life cycle, and they can produce up to five generations a year, depending on the temperature.

(Figure from Amendt, Krettek & Zehner 2004)

The female lays batches of 150-200 eggs in open wounds, rotten meat, or bodies. These eggs can hatch almost immediately after being laid, but they can take up to 9 days to hatch at 5 oC. The maggost will start feeding immediately. As the duration of each of the three larval stages depend on the temperature and is known in great detail, the age of the oldest maggots together with the average arrival time of the species allows to estimate the post mortem interval and approximate time of death.

Bluebottles will enter houses and lay batches of eggs in exposed meat either cooked or raw, and their attraction to rubbish makes them very abundant in cities. Bluebottles have an important ecological role as carcass decomposers...

... but they are also pollinators of several plants with exposed nectaries, such as ivy, spurges (Euphorbia) and plants from the carrot family. Some companies have even used bluebottles for greenhouse pollination of various crops as they fly at lower temperatures than bees. They also act as dispersers of fungal spores, and some fungi, like Stinkhorns (Phallus impudicus) have specific adaptations to attract blowflies, releasing chemicals that smell like rotting meat. The flies feed on the surface on the fungus and the spores attach to the fly, which can disperse them.
Next time you are annoyed when a bluebottle enters your house, you might want to give a thought to how useful these flies are.

More information
Amendt, J., Krettek, R., & Zehner, R. (2004). Forensic entomology. Naturwissenschaften, 91 (2), 51-65 DOI: 10.1007/s00114-003-0493-5

Donovan, S., Hall, M., Turner, B., & Moncrieff, C. (2006). Larval growth rates of the blowfly, Calliphora vicina, over a range of temperatures. Medical and Veterinary Entomology, 20 (1), 106-114 DOI: 10.1111/j.1365-2915.2006.00600.x

How do bugs cope with winter?

2011-12-05T21:35:00.000Z

We've had a couple of frosts in the last few days. Despite the die-hards which allow me to post occasionally these days, most insect species are nowhere to be seen throughout winter. How and where are bugs surviving the cold weather? There are various ways in which invertebrates go through the winter.

Far, far Away
Some - I'd say the lucky ones, avoid winter altogether - they are far, far away during winter, having migrated to warmer areas around the Mediterranean. These include several butterflies, moths, hoverflies and dragonflies (Red Admiral, Painted Lady -above - Silver Y and the Migrant Hawker are examples) which often lack a frost-resistant stage in their life cycle.

Slowing Down
Others stay to brave the elements, a few of them even carrying on more or less as normal, but at a much more sluggish pace. These are the invertebrates that enjoying the occasional sunbathing during rare winter sunny spells: Bluebottles (above), Winter Gnats, the window spider (Zygiella x-notata). Some moth caterpillars, like the Ruby Moth caterpillar, are found active in the middle of winter. A few bumblebee populations are starting to behave this way as the climate warms and they can make use of winter flowering resources.

Hibernating
Many insects enter diapause: this is the scientific term to describe what we often call 'hibernation': organisms enter a physiological state in which growth and feeding pretty much stop, and metabolism is very reduced. To protect their bodies against the damaging effects of freezing, some chemicals (glycerol and anti-freeze protein are two of them) are produced in their bodies to maintain cell stability and aid survival under low, often freezing, temperatures. Overwintering can occur in any stage of the life cycle depending on the species or taxonomic group - egg, larva or nymph, pupae or adult (imago).

The beautiful blue silk cocoon of a Enophlognatha spider, ready for winter.

For example grasshoppers, aphids and many spiders overwinter as diapausing eggs. Many dragonflies and damselflies overwinter underwater as nymphs. Many solitary bees overwinter as pre-pupae in their nest cells.

A fully developed Noctua moth caterpillar in early spring

Some butterflies and flies hibernate as pupae, whereas some butterflies (Comma, Small Tortoiseshell, Brimstone), Ladybirds, queen wasps and queen bumblebees hibernate as adults. Many solitary bees are already imagos in their cells, waiting for the right time to emerge.
I will keep my eyes open for bug life throughout the winter and be on the lookout for any stirrings indicating that springs is coming.

A little red underwater planet

2011-11-30T22:28:00.004Z

I have brought a few animals from my half barrel (=mini pond) to see close up to a small tank. Most of them are detritus feeders or vegetarians, and regularly I top up the tank with fallen leaves. Today's water was stained red and the reflection of the light in the water and the leaves made the photos take a surreal tint. A Great Pond Snail (Lymnaea palustris) fed on the algae growing on the tank walls (above).

Another snail, Planorbis planorbis

A group of ostracods, small bivalved crustaceans, and a copepod towards the left of the image.

There are also a few water slaters and planarians, but they didn't show as well today.

UPDATE: Thank you to Richard Comont for the pond snail ID, now corrected.

More information
Online aquatic snail identification guide from the Conchological Society. here.

Leaf sleepers

2011-11-26T19:47:00.000Z

This is a good time of year to search for bugs in the leaf litter. On the top layer, ladybirds are set for the winter in the cosy, dry folds of the fresh fallen leaves. They usually cuddle up close to other ladybirds of the same species to overwinter, but it is not unusual to see two species together, like the 22 spot and 7 spot above. If you search a bit deeper on the soil, you can find centipedes, earthworms, and woodlice. With the colder temperatures, they are more torpid than usual, and then easier to photograph.

A shiny woodlouse, Oniscus asellus

Centipede, Lithobius forficatus

A group of 22 spot ladybirds inside a vine leaf

Arion sp. slug

7 spot ladybird and birch shieldbug

Freshwater Flatworms

2011-11-25T22:02:00.002Z

If you kneel down on the edge of a clear water pond and look towards the bottom, even at this time of year, you might be able to see some flattened elongated creatures slithering over the sediments, like they are levitating (above). They are planarians or flatworms. On closer inspection they have a quizzical look due to their simple eyespots or ocelli, which appear to be both looking inwards. They are relatively simple organisms, which move over a carpet of cilia and have simple guts, with a single opening, the mouth, which is sometimes placed in the middle of the body. I am trying to get some shots of water slaters and I have set up a little tank at home. Most of the time when I get some decaying leaves from my half barrel (=minipond) a few flatworms are accidentally transferred with them, and then I can take some photos of them while they climb on the walls. There appear to be several species, but yet have to find out some resources to tell them apart.

One of the most striking features of flatworms is their capacity for regeneration. If you cut them in half, each half grows the missing parts. Even a tiny part of a planarian can regenerate a complete individual.

Centipede on a walkabout

2011-11-22T21:40:00.000Z

It is long, I counted 76 pairs of legs! My young daughter spotted this centipede, Stigmatogaster subterranea, walking on a stone wall out in the open. This is the first time I see this behaviour in this otherwise soil and leaf-litter living centipede. When disturbed, it had no trouble walking backwards, which had me puzzled for a bit, as I confused the tail and the head end!

The centipede lifted its head as if sniffing...

...and finally disappeared in the leaf litter.

Foggy morning

2011-11-20T22:12:00.000Z

The fog painted the spider webs hanging from bushes and fences this morning with pearly dew drops. It made evident that at least three spider species are still active. On the photo an Araneus diadematus web, we also saw Zygiella x notata and Linyphia triangularis webs.

Winter bees on Mahonia

2011-11-19T22:05:00.000Z

A lovely, still sunny day, I walk to a clump of Mahonia on a corner of an avenue. I have posted about this bug magnet in previous years (here, here and here) At this time of the year, Mahonia (Oregon Grape) is on bloom, its sweet scent and profuse, sunny-bright yellow flower spikes attract all late nectar lovers. Today, the bushes were busy, Bluebottles, Drone flies, honeybees and three (!) bumblebee species were feeding on it. A Bombus pratorum queen about to land, with a dronefly on the foreground on the top photo. This is one of the garden plants that are likely to have contributed to favour winter colonies in bumblebees. Bugs love this bush, and so do I.

Bombus terrestris queen. I have seen a worker this week too.

Bombus hypnorum

Honeybee

Dronefly and bluebottle

Pond Skater

2011-11-18T22:31:00.002Z

One of my earliest bug memories is watching pond skaters moving effortlessly and magically over the water. Pond Skaters, Gerris sp., also known as Water Striders, are true bugs: they piercing mouthparts are used to suck the juices of the insects they predate. Their legs are clothed with water-repellent hairs and they propel themselves with their middle legs in a flicking glide. Their front legs are small and kept tucked ahead of them, sensing the vibrations in the water from other ponds skaters or potential prey that have fallen in the water, and also grasping and holding their prey. They are seven similar species of Pond Skaters in the U.K., and they are sometimes found in the same pond. Pond skaters are active in these mild days of autumn and will overwinter as adults, moving away from the water with the first frosts. Many pond skaters species are polymorphic and have long-winged and short-winged morphs. In species with two generations per year, the long-winged form tends to be the overwintering generation - which is also the dispersive one - while the summer generation tends to be short winged. When the winter comes, short-winged individuals, unable to fly, will crawl out of the water and hide in the bank, while long-winged ones can fly away from water, to sites that are free from risks of flooding or freezing. In the spring, emerging pond skaters will fly back to ponds and lakes, using the reflections of the water - or other shiny surfaces - as guide.
Pond skaters, as other true bugs, go through five instars before becoming adults. The individual of the top photo is a nymph (24 Jun 2011), the one at the bottom, an adult (2 Jul 2011). Although the photos are from earlier in the year, smaller nymphs were still in a local pond last monday.

The Great Ramshorn Snail

2011-11-17T21:46:00.002Z

There is still a lot of activity in ponds. We haven't had a frost yet and Pond Snails, water-lice and ponds skaters go about their lives as usual. This is a Great Ramshorn Snail, Planorbarius corneus, inhabitant of still or slow moving waters with a high calcium content and plenty of vegetation. Unlike land snails, Ramshorn Snail's eyes are at the base of their long tentacles. They graze algae and plants or feed on dead leaves. They are hermaphrodite, although they prefer to cross-fertilise one another. They will lay their gelatinous egg batches on the underside of leaves. I photographed it on the white bowl with some rain water.

Is global warming erasing a melanism cline?

2011-11-16T22:20:00.001Z

The 2 spot ladybirds, Adalia bipunctata, I find in my garden are of the typical morph, red with 2 black spots, one in the centre of each wing case, but there is also a melanic morph in this species* - black with four red spots - and several rarer intermediate morphs, which are determined genetically. Some colour morphs tend to be more common in some areas than in others. This geographic variation is thought to reflect differences in temperature regulation between morphs. Melanic ladybirds benefit from thermoregulating more effectively in certain microclimates: when there is little, intermittent sunshine and is colder. This advantage becomes most important in early spring, when after emerging from hibernation ladybird behaviour is strongly limited by temperature, so the black ladybirds can start reproducing earlier. Paul Brakefield and Peter de Jong have studied the polymorphism in the two spot ladybird in Holland for 30 years. The two spot colour polymorphism, nicely matched the differences in climate between the warmer coast and the colder inland areas. At the beginning of their study period, in 1980, the dark morph was commonest inland, where it reached 60%, and its frequency decreased gradually towards the coast (less than 20%). Samples taken in the same transect since then show how the sharp decline in frequency of the dark morph gradually disappeared to the point that there was little if no differences between sampled areas in 2004, with the frequency of the melanics in inland areas dropping to similar levels than the frequency in coastal areas. Brakefield and de Jong think that the disappearance of this cline is a response of the ladybirds to the gradually warming climate in the area.

Figure 1 Changes over time in the proportion of the illustrated melanic and non-melanic morphs of the two-spot ladybird beetle along a transect of ca. 115 km in length in the Netherlands (bottom-left). Samples were collected in each of the 5 years indicated at 16 more or less evenly spaced localities from west to east. Colouring of years matches the histograms for melanic frequency in the individual samples from each locality. The panel on the bottom-right shows deviations in average temperature from a ‘normal’ season/year at De Bilt (red spot on map). From left to right, columns represent data for winter (Wi), spring (Sp), summer (Su), autumn (Au) and the overall year (Tot), respectively, and from top to bottom for different years beginning before the period of ladybird sampling. The colour of each block indicates the extent to which the average temperature in the particular season/year deviated from ‘normal’; white, no deviation, blue, cooler than normal (dark blue more extreme than light blue), red, warmer than normal (dark red more extreme than light red)(from Brakefield & de Jong, 2011)

The story has a second dark aspect. The researchers had trouble reaching acceptable sample sizes in the 2004 sampling season. They even failed to find 2 spot ladybirds in two localities where they previously had been abundant. They attribute the decrease in numbers of the 2 spot ladybird to the impact of the invasive harlequin ladybird, which reached Holland in 2002. Not only the melanism cline is gone, but the 2 spot seems to be dissapearing as well.

References

Brakefield PM, & de Jong PW (2011). A steep cline in ladybird melanism has decayed over 25 years: a genetic response to climate change? Heredity PMID: 21792220

*UPDATE
So it seems I do have melanic 2 spots in the garden (above). Thank you to Helen Roy, who curates the Ladybird survey site for the ID.

The Migrant Hawker

2011-11-14T22:42:00.001Z

The Migrant Hawker, Aeshna mixta, is one of the commonest dragonflies found away from water. It regularly visits my pond-less garden, with a clearly marked peak in the second half of August (the male on the top shot from 15th August this year). This species is a fast developer, their larvae take just a year to become adults, but it is sensitive to the cold. Adults are not territorial and are often found hunting together, at high, patrolling over the garden hawking for insects. Early in the morning they rest hanging from vegetation, sunbathing, at about 1-2 m high, often a pair not far from one another, and they then allow close approach.

A female Migrant Hawker basking, with another individual on the background (16/08/06) - which I only noticed when checking the photos.

Although dragonfly migration has been known for over a century, it is still a little known phenomenon. Several British dragonfly species are regular long-distance migrants, like the Four Spotted Chaser and the Common and Ruddy Darters, and others occasionally appear as vagrants from the Mediterranean or even from North America. Where do they go and why do they do it? Do they migrate back and forth or do they just wander? Is this behaviour to avoid overcrowding or drought, in search for good sites for reproduction? David and Elizabeth Lack (1951) favoured the existence of large scale two way migration in dragonflies, like that of many birds and butterflies, after observing large numbers of Common Darters passing over a high mountain pass in the Pyrenees. American migrants tend to be species breeding in ephemeral or semipermanent ponds, which dry frequently, so migration might also be a wandering in search of suitable ponds. Recently, a combination of miniaturised radio transmitters, isotope analysis and genetic markers have shed light into the migratory behaviour of the American Common Green Darner, Anax junius. Although the Migrant Hawker has been seen forming large swarms, unfortunately, we know very little about the migration in this species. In any case, its migratory behaviour makes it a very good coloniser. In the early 20th century it was regarded as a rare immigrant - in fact it was called Scarce Hawler -, but singe an invasion in 1935 it has been steadily and rapidly expanding its range northwards and westwards in the UK, reaching Scotland in 2004. The species also colonised Ireland in 2000 and is now well established. I can't wait to find out more about these fascinating garden visitors.

References
Wikelski, M., Moskowitz, D., Adelman, J., Cochran, J., Wilcove, D., & May, M. (2006). Simple rules guide dragonfly migration Biology Letters, 2 (3), 325-329 DOI: 10.1098/rsbl.2006.0487

Lack, D. & Lack, E. (1951). Migration of Insects and Birds Through a Pyrenean Pass The Journal of Animal Ecology, 20 (1) DOI: 10.2307/1644

E.S. Dyatlova & V.J. Kalkman (2008). Massive migration of Aeshna mixta and Sympetrum
meridionale in the Ukrainian Danube delta (Odonata-Anisoptera: Aeschnidae, Libellulidae) Entomologische Berichten, 68, 188-190

Brian Nelson, Colm Ronayne & Robert Thompson (2003). Colonization and Changing Status of Four Odonata Species, Anax imperator, Anax parthenope, Aeshna mixta and Sympetrum fonscolombii, in Ireland 2000-2002 The Irish Naturalists' Journal, 27 (7), 266-272

How to get a snail to go aaaaah!

2011-11-13T17:01:00.000Z

I have spent quite a lot of time lately tidying up my photo library and tagging photos and I have come across several worth posting about even if they won't be as timely as usual. I wanted to see if I could take some shots of snail's mouths. To do this, I mashed up a few dandelion leaves and painted an area of the outside of one of the conservatory window with the resulting concoction. Then I found a few active snails and this one delivered. It started climbing up the window, its foot showing the muscular ripples that power its slow advance, mouth shut tight.

As soon as the snail felt the dandelion mixture, it opened its mouth and started licking it, showing its tongue (the radula) and the chininous, dark hardened ridge in front of it. The radula is a muscular organ covered in rows of hard little teeth that can scrape surfaces and it was very evident how the snail used it to eat the bits of the dandelion leaves once it got to them.

Dandelion leaves, yum!

These are the marks left by snails or slugs while grazing algae growing on a pot

The snail also showed nicely the opening of its lung, on the right side of its body.

A wrapped up genetic legacy

2011-11-13T16:12:00.000Z

There are still fresh garden spider webs around if you look, with large Araneus diadematus females making the best of the mild weather. Many, though, have now died, exhausted and shriveled up, after laying eggs. This genetic legacy to next year generation is now inside wrapped up in a yellow silken cocoon attached a corner sheltered from the rain. After finishing their cocoon, they sit on it until they died, not bothering to make a web any more. The eggs will overwinter inside the sac and the spiderlings will emerge the next spring.

30 October 2011, female spider on her egg sac.

Autumn colours

2011-11-12T16:38:00.004Z

This moth caterpillar was ready for the winter when I disturbed it. I used a cherry leaf as a background. The garden spider below had hung her web in front of the rowan, so I could take advantage of a clump of berries as background.

The face of the alien aphid muncher

2011-11-09T17:09:00.000Z

This Harlequin ladybird happily eating an aphid on the 6th of November illustrates how active many of these ladybirds still are. I found young and old larvae, pupae, mating adults and already hibernating adults in a small area near in my local park. Harlequins are multivoltine, and will carry on reproducing as far as conditions are suitable. In northern Europe, two generations and possibly three if weather conditions allow can occur, as adults do not need to hibernate before they can reproduce, as it is the case with the 7 spot ladybird.

Little riders on the wind

2011-11-07T22:03:00.002Z

The mass influx events of Painted Ladies - such as during the summer of 2009 - and wildlife documentaries on the Monarch Butterfly have made butterfly migration familiar to everybody. Many butterfly species are now known to carry out bidirectional migrations, for those of the northern hemisphere, towards the north in the spring and towards the south in the autumn. Surprisingly, the extent of fascinating behaviour was only recognised relatively recently. Up to the 1930s, the only butterfly that was acknowledged to migrate was the American Monarch, Danaus plexippus, with evidence for migration in other species dismissed even from experienced entomologists and lepideropterists as "overflow": one way dispersal movements from successful, very dense populations. One early researcher was set to change matters: Carrington Bonsor Williams (widely known as C.B.), from Rothamsted Experimental Station in the U.K. He was passionate about insect migration and amassed large amounts of data on the subject, in Britain and abroad. In his 1930 book Migration of Butterflies and later work, he presented evidence for migration for over 200 species of butterflies worldwide, including support for return migration. He also helped organise the collation of data collected by naturalists across the U.K. on insect migration. His analyses of these data gave strong evidence for migration for six species of British butterflies: the Painted Lady, Small Tortoiseshell- which also hibernates in the U.K. - , Red Admiral, Large White, Clouded Yellow and Pale Clouded Yellow. For the Red Admiral, the records showed clearly a dominant proportion of individuals flying in a northerly direction up to the end of July, and a southerly direction during September and October:

(Figure from Williams 1951)

In the case of the Painted Lady and the Large White, the lack of evidence for a return migration puzzled Williams:

I have already (Williams et al. I942, p. 250) pointed out the difficulty of accounting for the persistence of a habit of movement in one direction only on any theory of evolution. If we accept that directional movement in butterflies is simply an overflow from an over-populated area, and that none of the emigrants ever return; then the species must be perpetuated by the offspring of those individuals which do not emigrate. Thus a habit must persist for countless generations, in spite of the fact that all individuals which develop it die without contributing to the continuity of the species.

He was optimistic though, and correctly predicted that return flights would be found in all species once enough research effort was put into it, making butterfly migration as important a phenomenon as that in birds. Indeed, recent research - some of it carried out in Rothamsted - including meteorological analysis of prevailing winds when influxes of Painted Ladies occur, and entomological radar research has shown that the Painted Lady taked advantage of tailwinds as a migratory aid and that the reason that these flights were not detected is that they fly at high altitude.
Migrating butterflies are tracking suitable breeding grounds, areas where larval food plants are abundant. Red Admiral caterpillars feed on fresh, rapidly growing nettles. At the end of spring, nettles start to wither in the Mediterranean winter grounds, so the spring Red Admiral adult generation flies to Northern Europe - and also up mountains - where nettles are luscious. They mate and lay eggs in the north and the resulting autumn generation of adults migrates due south in the autumn.

(Figure from Mikkola 2003)
Unlike birds, butterflies breed both in the winter and summer grounds, and also unlike birds, each generation makes a one way trip, leaving the return journey to their offspring.
(Photo above, a fresh, autumn generation Red Admiral feeding on Cherry Laurel, 19 Aug 2011)

References
Williams, C. (1951). Seasonal Changes in Flight Direction of Migrant Butterflies in the British Isles The Journal of Animal Ecology, 20 (2) DOI: 10.2307/1537

Kauri Mikkola (2003). The red admiral butterfly (Vanessa atalanta) is a true seasonal migrant: an evolutionary puzzle resolved? European Journal of Entomology, 100, 625-626

Stefanescu, C., Alarcon, M., & Àvila, A. (2007). Migration of the painted lady butterfly, Vanessa cardui, to north-eastern Spain is aided by African wind currents Journal of Animal Ecology, 76 (5), 888-898 DOI: 10.1111/j.1365-2656.2007.01262.x

Chapman, J., Nesbit, R., Burgin, L., Reynolds, D., Smith, A., Middleton, D., & Hill, J. (2010). Flight Orientation Behaviors Promote Optimal Migration Trajectories in High-Flying Insects Science, 327 (5966), 682-685 DOI: 10.1126/science.1182990

A november gift

2011-11-06T21:25:00.002Z

Each passing day is shorter and with a weaker sun than the previous one, and each Red Admiral sighting feels like a lovely gift. This afternoon, a battered individual sat basking on the fence, cleaning its head, with its body and wide open wings angled, casting a long shadow, capturing the maximum warmth of the sun. After a few minutes, it fluttered to the Erysimum and fed on it. For a while, it alternated feeding - later on the flowers already in the shade - and warming.

The maladapted parasite

2011-11-05T23:51:00.003Z

There is a corner in my local park which is always teeming with Harlequins. At this time of the year adults ready to hibernate and grown larvae about to pupate dot the railings and fenceposts. A couple of days ago I came across this individual dragging a strange large lump behind as it sluggishly walked on top of a railing. I took a photo and wondered if it was a parasite. Parasites in Harlequins are very interesting, as, this ladybird being an invasite species, they might be adapting to the newcomer and helping keeping this species in check. Richard Comont, from the Centre for Ecology and Hydrology in Wallingford, after checking the photo commented:

It looks like a Dinocampus which has got caught up in the ladybird's wings - I think you can just about see some segmentation at the bottom of the yellow lump. Dinocampus seem to be a bit disorientated in Harlequins - they seem less able to fully paralyse the adults on the way out - so possibly might sometimes emerge from the top of the abdomen, from between the tergites rather than the sternites, which could result in the emerging larva ending up in the wing like this.
Dinocampus, on emerging, usually parasitise their host ladybird, cutting the nerves connecting the legs to the nervous system, and potentially also the tendons of the leg abductor muscles which allow the ladybird to move its legs away from its body (so that when the parasitoid's cocoon is spun between the ladybird's legs it can only be clutched tighter). However, Harlequins with Dinocampus are often not fully paralysed, and instead stumble around slowly, almost drunkenly.

It appears that some native ladybird parasites are also attempting to parasitize the newcomer invasive Harlequin, which is encouraging. Evolutionary success for parasites in expanding their host range to include Harlequins however, will only come if the parasite is successful completing its life cycle in the new host. The offspring of the parasite must actually be able to become a successfully reproducing individual in the new host, and the disorientation of the Dinocampus in Harlequins, which could often result in their larvae being unable to spin its cocoon under the host - which is walking around dragging it - suggests that their success in surviving and actually becoming an adult parasite might still be far lower than in the native ladybirds. They still might have some way to go.

I am most grateful to Richard Comont for allowing me to reproduce his comments in this post and to Lori Lawson Handley for kindly forwarding my photo to some knowledgeable ladybird experts.

UPDATE
From an e-mail from Richard Commont (15/11/11):

I’ve found a couple of these ‘parasitised’ Harlequins today – and the ‘parasite’ was just a pool of reflex blood, which the wing had folded around into a kind of bag – no evidence of parasitism at all!

That's science for you!

Queens, harlequins and admirals

2011-10-30T21:18:00.001Z

The last mild, sunny days of autumn are bringing out scores of insects. Standing under a large flowering ivy today the sound of buzzing bees, bluebottles, droneflies and wasps was extraordinary, especially given that November is only a couple of days away. Yesterday, six red admirals sunnied and gorged themselves on the ivy blossom. They are charging batteries before their migration to South Europe and North Africa.

Red Admiral and passing droneflies on ivy

A green shieldbug, Palomena prasina, climbing a tree.

Today, a queen Bombus hypnorum fed on lavender flowers.

A female Araneus diadematus spider sat proudly on her silky egg cocoon.

Honeybees on ivy flowers

Dozens of harlequins and 7 spot ladybirds flew about landing on a sunny wall and leaving again.

Ready for winter

2011-10-22T19:14:00.000+01:00

Only a couple of weeks ago, 7 spot ladybirds were mating. Today we found this little cluster, with a harlequin trying to merge in, nestled on a wall, ready for winter. More BugBlog ladybird posts here.

Mating 7 spots on 9/10/11.

The singing lacewings

2011-10-21T17:21:00.000+01:00

Adult common green lacewings, Chrysoperla carnea, are starting to search of suitable hibernation places, and they often come inside buildings. This one was inside my office the other day and allowed me to take her portrait. C. carnea was once thought to be a single widespread species but it is now known to be a species complex, an aggregate of morphologically very similar species that often co-exist. Courtship involves males and females drumming a song on the substrate where they are sitting with their abdomens. The vibrations are detected by organs in their legs. Males and females respond to each other's drumming in a complex duet and only when they sing the same song does the courtship ends in mating. The different species in the complex have different songs, with characteristic drumming frequencies. The figure below illustrates the differences between the six biological species within the C. carnea group that are recognised in Europe.

The drumming songs of European cryptic species of Chrysoperla carnea sensu lato (from Henry et al in
Lacewings in the crop environment By Peter K. McEwen, T. R. New & A.E. Whittington)

Both C. lucasina (probably the top photo) and C. c. 4 "motorboat" also known as C.c. "sensu stricto" have been found in the U.K. Lucasina does not change colour in winter, has "pointy wings" and a dark membrane between the sternites and tergites in the abdomen. C. carnea sensu stricto has rounded wings, changes colour and does not have the dark membrane. However, individuals that do not fit either of the species are often found in the U.K.

As their distinctive songs are difficult to tell apart for the untrained eye (ear?), and the morphological characters that do differ between the cryptic species are sometimes not apparent or distinctive enough, identification to these lacewings on the field is tricky.

C.c. 4 "motorboat" may change colour prior hibernation (photo from 10 October 2011).

Lacewing larvae, distinctive large jaws and covered on detritus, which often are the shriveled skins of the aphids she feeds on.

Earwigs and the conundrum of cryptic species complexes

2011-10-16T23:29:00.001+01:00

While collecting grapes, I came across a group of adult earwigs. Earwigs are insects of the order Dermaptera, characterised by the presence of a pair of sexually dimorphic appendages at the end of the abdomen called forceps. Female forceps are more or less straight (above), while the male's (below, with two males of different sized forceps) are larger, curved and furnished with a pair of teeth. F. auricularia males are also dimorphic, with a large forceps form (macrolabic) and a small forceps form (brachylabic).

Earwig forceps are used for defence - they readily raise their forceps when disturbed - and are involved in reproduction, males fight using their forceps as weapond and display them to females during courtship. Males with larger forceps seem to be preferred by females, so they appear to have evolved through sexual selection. Earwigs are also unusual amongst insects in their level of maternal care. Females build a nest chamber, and stay with their eggs after oviposition, they continuously groom their eggs keeping them fee from fungi and sit atop them, occasionally moving them within the nest to areas of optimal temperature and humidity conditions. They also provide their larvae with food and defence for several instars. In 1998 Thiery Wirth and colleagues, while examining the inheritance of brood number variation in the common European earwig Forficula auricularia through laboratory crosses, found that single brooded and two-brooded forms did only rarely produce offspring. Further genetic analyses confirmed that F. auricularia is made of two cryptic species. Cryptic or sibling species are species that cannot be distinguished easily by their morphology, although they are reproductively isolated and might differ in song or pheromones so, despite their similarity to our eyes, males and females do not recognise each other as mates. Cryptic species are very common among many invertebrate groups and are a nightmare for the biologist trying to understand the behaviour or ecology of a species, as it is often impossible to be sure that one is dealing with a single species without using genetic tools. In F. auricularia, the two cryptic species have not been formally described, but one, referred to as species A, prefers colder climates or higher altitudes, females are single brooded, and tend their clutch for longer and the larvae disperse later; while species B typically lives in more temperate areas, females produces two broods, tends its brood fo r a short time and has an earlier larvae dispersal. In his PhD thesis, Gordon Brown concludes that a single species inhabits the UK, and this is the single brooded species A. At this time of the year, males and females are found above ground and they will be mating. Although males stay with the female and may help with nest building, they are unlikely to make it through the winter and are excluded from the nest once oviposition takes place, while females will overwinter in the nest, where they will lay their eggs early in the year and tend the next generation of earwigs.

References
Guillet, S., Guiller, A., Deunff, J. & Vancassel, M. (2000). Analysis of a contact zone in the Forficula auricularia L. (Dermaptera: Forficulidae) species complex in the Pyrenean Mountains. Heredity, 85 (5), 444-449 DOI: 10.1046/j.1365-2540.2000.00775.x
Thierry Wirth, René Le Guellec, Michel Vancassel & Michel Veuille (1998). Molecular and reproductive characterisation of sibling species in the European earwig (Forficula auricularia) Evolution, 52 (1), 260-265.
Gordon Brown (2007) Sperm competition and male forceps dimorphism in the European earwig Forficula auricularia (Dermaptera: Forficulina). PhD Thesis University of St. Andrews.

Spider beetle

2011-10-16T21:05:00.000+01:00

I found this tiny spider beetle, Ptinus sexpunctatus in the bath today. The second time I see this species, both times found in the bathroom. The name spider beetle comes from the long legs and antennae of the beetle and its tucked-in head, which makes them resemble a spider superficially. They feed on decaying insects and are often found in bee nests, presumably feeding on the pollen/larvae.

Late bumblebee collecting pollen

2011-10-16T20:40:00.001+01:00

It is not unusual to see bumblebees in Autumn. Queens are still about, storing up some reserves before hibernation. What I found unusual is a worker of a Bombus pascuorum collecting pollen in my patch of Lamium maculatum today. The bumblebee visited each flower inserted its head deep into it and as exiting, wiped its furry back with its rear legs collecting the pollen on its corbicula or pollen basket. I understand that bumblebees collect pollen for their larvae, so there must be still be B. pascuorum active nests this late in the year.

The curious Autumn spider mating tactics

2011-10-14T22:26:00.000+01:00

Female spiders tend to be larger than males. Large females are thought to be selected for as they can produce more eggs. The relative size differences between males and females depend on the type of competition between males, that is, on the importance of intra-sexual selection. When males do not compete much with one another they are smaller than females, whereas when there are male-male contests fr females, then large males are selected for and size differences with females become smaller. The spider, Metellina segmentata, is an orb spider common during september and october, when most mature individuals are found. Males are more powerfully built and have longer legs than females, suggesting that male-male contests occur in this spider. When young, males build their own webs to hunt insects, but upon reaching their final moult, they mature and start searching for female webs. Once they encounter a receptive female web - likely through detecting a pheromone - they adopt a curious sit and wait strategy. They have to wait, often days, until a large fly falls in the web. Only when the female starts eating the fly does he starts his courtship, taking advantage of the diminished cannibalistic tendencies of sated females. Of course, during this wait, other suitors might arrive to the female's web and when two males encounter each other fights follow. Males are often injured or killed in these fights, where the larger male has an advantage and this is what provides the selective pressure for powerfully built males.
In addition, males are able to monitor several female webs when they are nearby and this results on males guarding webs become larger as the season progress, and a pool of smaller wandering males.
The mature female Metellina on the top photo has hung her web on a tomato plant since at least mid september. I haven't noticed any males but I shall keep an eye for these in the next days.

Reference
Prenter, J., Elwood, R., & Montgomery, I. (2003). Mate guarding, competition and variation in size in male orb-web spiders, Metellina segmentata: a field experiment Animal Behaviour, 66 (6), 1053-1058 DOI: 10.1006/anbe.2003.2266

BugBooks: Chinery's Insects

2011-10-08T19:38:00.000+01:00

Given that the oncoming months will, by necessity, subdued at BugBlog, I have decided to start a new section. I will present and review my favourite books on British bugs, books that I routinely use to find information or to identify the bugs that feature in BugBlog. Please feel free to comment with your own favourites. My first choice has to be undoubtedly Michael Chinery's Insects of Britain and Western Europe, a very informative, superbly illustrated field guide. An additional advantage is its size, soft bound and small. Its 320 pages are absolutely packed with information, including distribution pattern in Western Europe and in Britain, time of the year where they are found, behaviour and habitat. The colour illustrations are superb, detailed and accurate. Many species are illustrated with adult and caterpillar or larvae and the illustrations often shows common behaviour. A key at the beginning of the book will help you identify what group an unidentified insect belongs to. At the end of the book, there is a section with a selection of species of non-insect arthropod groups such as Spiders, Woodlice, Millipedes, Centipedes Scorpions and Harvestmen, which comes in handy.
My copy from the reprinted first edition in 1986, is getting dated. Since it was put together, many new species have arrived to the British Isles and have become now common and are not described (e.g., the ubiquitous Harlequin or the Horse Chestnut Miner). In addition, the distribution of many other species has significantly shifted northwards (e.g Speckled Wood, Comma) or they have moved to the U.K. from the continent (Tree bumblebee, Ivy Bee). But those are minor quibbles, I couldn't do without this book. There is a more recent revised edition (2007), which is a bit pricey. A proviso, this book does not include all species of European insects (there are over 100,000 described), but a selection of the most common or noticeable. Once you become familiar with an insect group - be butterflies, hoverflies or dragonflies - you will require a specialist guide.
Overall, a must for the bug lover.

Two white plate orb spiders

2011-10-05T20:56:00.001+01:00

The garden is scattered with orb spiders, including the ubiquitous garden spider Araneus diadematus (above) sat in the middle of their webs during the day, and females, now laden with eggs, are very obvious. But there is a smaller species of orb spider can easily pass unnoticed despite being common in gardens, its the beautifully named, more delicate Metellina segmentata, also known as autumn spider (below). It has longer front legs, and there is a round empty space in the middle of her web. But days are shorter and the sun not as strong, and I miss natural light when taking photos. The orb spiders pose a challenge for my usual white bowl spider portrait technique: they are not walking spiders, and they are at their most comfortable hanging from their webs. So, for these shots of spiders in the garden I replaced my usual white bowl by a large white plate, which I carefully held behind each web while I took their portraits.

Knowledge is power for the sun spot owners

2011-10-04T21:37:00.001+01:00

Even as the butterfly season comes to an end, Speckled Wood butterflies, Pararge aegeria, are still going strong in my local overgrown cemetery. The hundred year old trees, shade the ground and sunny clearings are highly prized by Speckled Wood males. Yesterday, I watched them squabbling incessantly in a patch of grassy area amongst the trees. At some point, the resident male chased two other individuals, the three butterflies flying around in tight circles away from the prized spot. Another individual comes by oblivious to the ownership contest and takes possession of a sunny dock leaf in prime position (above). By the time the initial "owner" comes back victorious from the skirmish, the newly arrived one believes this is his spot and the subsequent squabble ensues. It is really never ending in this warm autumnal morning with the sunspot owners.
What determines how is the fight settled? In the late 1970s Davies work suggested that prior ownership is a very strong predictor of success in a fight: residents always won. Later work by Christer Wiklund and collaborators have expanded and refined Davies' findings, indicating that although a good predictor, ownership is not the only factor involved in territorial fights. Age and size are factors that are known to be predictors of fight outcome, but in the Speckled Wood these have little importance. Martin Bergman, Martin Olofsson and Christer Wiklund investigated the effect of motivation on territorial fight outcome. Residents might be more motivated to fight because they have more information on the value of the resource they are fighting for: the resident male might have prior mating experience in that spot, or knows how prized the spot is for other males. The intruder, most of the time lacks such information. This creates an asymmetry in which the resident is more determined to fight than an intruder.
To test this hypothesis, the researchers set up experiments in large outdoor cages with a prime large sun-spot, and smaller, suboptimal sunspots. They released two males in each cage and waited until there was a clear dominant male that took possession of the large sunspot. They they removed the dominant male and divided the subordinate males in two groups, half of the males repeatedly encountered a female during a 30 min residency period (female encounter group), while the other half (the control group) did not have any female encounters. Then they tested the effect of this prior experience - motivated vs unmotivated males - on contest outcome when they introduced the original dominant individual back in the cage. The results were very clear.

Outcome of contests between Speckled Wood males during the second contest period when the original winner had been reintroduced, and after the original losers had either interacted with a female during 30 min (female encounter group, n = 30) or been alone for 30 min (control group, n = 30); ‘reversal’ (open bars) denotes that the male that lost the contest during the first contest period reversed the outcome and won the contest against the original winner in the second contest period, and ‘no reversal’ (filled bars) denotes that the same male won in both contest periods (from Bergman et al 2010).

Half of the originally subordinate males won their fight with the original dominant in the "female encounter group". In contrast, most of the dominant males won their fight for the prime sunspot when no females had been present. Also, the fights in the treatment group were more intense and took longer to resolve, while the control group the fights were settled quickly. In conclusion, these experiments showed that male experience in a sun spot increase his persistence in a fight, and therefore increase the chances of winning it, even if he was initially a subordinate male, indicating that motivation is an important factor for contest resolution in the Speckled Wood.

References

Bergman, M., Olofsson, M. & Wiklund, C. (2010). Contest outcome in a territorial butterfly: the role of motivation Proceedings of the Royal Society B: Biological Sciences, 277 (1696), 3027-3033 DOI: 10.1098/rspb.2010.0646
Davies, N. (1978). Territorial defence in the speckled wood butterfly (Pararge aegeria): The resident always wins Animal Behaviour, 26, 138-147 DOI: 10.1016/0003-3472(78)90013-1

On the Western Conifer Seed Bug and Christmas trees

2011-10-01T20:11:00.004+01:00

This large, striking bug entered the house at night through an opened window. It is the alien species Leptoglossus occidentalis, the Western Conifer Seed Bug, a native from western North America, where is a minor pest of conifers. This species has long antennae and large rear legs, a pale zig-zag mark on the wings, and distinctly flattened and enlarged tibia, which gives the name to its group, the leaf-footed bugs. During last century, this species spread across North America and during the last decade has also been introduced in Europe, where it has quickly spread from the initial introduction point in Italy. It was accidentally transported in timber, and its spread could also possibly been aided by Christmas tree shipments. Nymphs and adults feed on the sap of cone seeds and buds, and therefore the damage is restricted to seed production. In continental Europe, where there are established populations, it does not appear to cause much damage. Every now and then, there are migratory influxes to the U.K. from the continent, as occurred in 2008. The bug often falls in moth traps, and is a good flyer. It is most obvious in the autumn, when it moves about looking for suitable hibernation sites, often entering buildings and sometimes forming large aggregations, attracted by pheromones produced by males. Nymphs have been found in a few sites in the U.K., so it appears to be establishing.
If you have seen this bug, you can report it here.

References
Lis, Jerzy A., Barbara Lis & Jerzy Gubernator (2008). Will the invasive western conifer seed bug Leptoglossus occidentalis Heidemann (Hemiptera: Heteroptera: Coreidae) seize all of Europe? Zootaxa, 1740, 68-68
Taylor, S.J., G. Tescari & M. Villa (2001). A nearctic pest of Pinaceae accidentally introduced into Europe: Leptoglossus occidentalis (Heteroptera: Coreidae) in Northern Italy. Entomological News, 112, 101-103.
Blatt, S. & Borden, J. (1996). Evidence for a male-produced aggregation pheromone in the Western Conifer Seed Bug, Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) The Canadian Entomologist, 128 (4), 777-778 DOI: 10.4039/Ent128777-4

Office jumping spider

2011-09-21T22:07:00.001+01:00

I watched this tiny jumping spider this morning crawling up my office wall. It must have been 4 mm in size. It carried its dark front pair of legs pointing forward, which gave it a crab like appearance, but its lovely face with large, front facing middle pair of eyes were unmistakable as a jumping spider. It was a male Pseudeuophrys lanigera male, a synanthropic species, that is, often found in or around houses.
The species originates from southern Europe, and has spread throughout Europe during the last century. In the UK is also expanding north.
Males have a striking combination of a red face mask, a white moustache, white palps, and robust, black front legs, females are a bit more subdued, and their front pair of legs is annulated as the others.

the male on top view

female (9/04/11)

same female on windowsill (9/04/11)

A tree bumblebee queen

2011-09-20T20:19:00.000+01:00

This tree bumblebee, Bombus hypnorum, queen has been visiting the garden in the last couple of days, with her fresh, striking tawny/black/white pattern very apparent. The last time I saw this species this year was in July, when males patrolled in the garden and queen bees could be seen searching for nest (or hibernation sites). August, three years in a row, yielded no sightings. Yesterday's queen visited Erysimum "Bowles's Mauve". This perennial wallflower, which often appears in BugBlog shots, and I highly recommend in any wildlife garden, has a very long flowering season and attracts a range of solitary bees and bumblebees, hoverflies and butterflies.

This graph shows the number of days per month I've seen this bumblebee in the last three years. Workers are active during May and June, most of the July activity is males marking and patrolling their flight paths and queens. The rest of the sightings in the autumn and early spring are queens feeding or nest searching.

The hoverfly nightmare

2011-09-18T20:19:00.000+01:00

Yesterday morning I found this Ectemnius wasp on a plant pot. Usually, they are very active and are flighty, but this one was still cold and let me take some close ups. Ectemnius are digger wasps that hunt flies - including hoverflies - for they larvae to feed. They dig a tunnel in wood and stock cells with flies, laying their eggs in them. They are several similar species, that can only be distinguished under the microscope. The microscope, however, is not needed to appreciate two of the weapons that these wasps use for hunting: their amazing, large, envolving eyes - note the antennae nicely folded between them, not occluding their field of vision, and their fearsome jaws, folded under their head.

A bit of slug romance

2011-09-10T22:12:00.001+01:00

As their snail relatives, slugs are hermaphrodites, each individual producing eggs and sperm. Although some species regularly self-fertilise, in many others, individuals - given the chance - will trade sperm with other individuals they encounter. I came across this pair of courting slugs under a fallen apple an evening last week. They are Deroceras panormitanum (thanks to Fauna, from WAB for the ID). At the right time of the year, and when meeting a potential partner, these slugs crawl in circles, producing and eating chemicals mixed in their respective mucus trails, before mating happens. The outcomes of courtship and mating are diverse: the slugs are able to mate repeatedly and use sperm from several donors to fertilise their eggs, or they might decide not to give sperm to its partner, or digest the sperm obtained and self-fertilise. This means that, despite being hermaphrodite, a slug can decide if to act only as male (digesting the partners sperm but providing its own), as female (refusing to give sperm, maybe preferring to save it for a better partner) or as both. This can create conflict between the partners - each with their own interests - and has been hypothesized to spur an "arms race" - or "genitals race" if you wish, and has led to the evolution of a range of bizarre copulatory structures and complex mating courtships.
Heike Reise has reviewed and described the behaviour of these diverse genus of slugs and summarized courtship and mating as follows:

(i) Precourtship phase: the partners encounter and investigate each other.

(ii) Courtship phase: both partners have their sarcobelum protruded from the genital opening and assume a position with their genital pores facing each other, forming a circle or yin-yang configuration.

(iii) Copulation phase: the slugs evert their penes, entwine them, and mutually transfer the ejaculates from penis to penis (there is no intromission).

(iv) Withdrawal phase: the penes are retracted together with the attached sperm masses.

After coming across a potential partner or trail, some following behaviour follows. This species has a flattened tail, which is enlarged during courtship and waved from sude to side. These movements increase the chances of contact with the partner's tentacles. If the leading individual is ready to mate, it eventually turns round and starts following the second individual, forming a circle. Both individuals then evert their sarcobellums - as seen in the top shot - a solid, mobile structure in the genitalia which produces chemicals, that are exchanged during their circling behaviour. The sarcobelum is very active during the courtship, tracking closely the partner tail end and stroking it, at the same time that smears the partner with chemical secretions. In this species, courtship can last over an hour, followed by a relatively quick copulation (a few minutes), in which the slugs genital openings become very close, actual penises - bluish, transparent masses - are everted and entwined with the partners and sperm are exchanged externally. These slugs also have a penial, multifingered gland, that they also evert after insemination and lay over their partner's back, transferring some secretions. The function of this gland has been suggested to be equivalent to the snails' dart, the smeared chemicals on the partner might increase the chances of paternity. The slugs above were in the courtship stage, but unfortunately, by the time I went out again to check on them, they had disappeared.

References
Heike Reise (2007). A review of mating behavior in slugs of the genus Deroceras (Pulmonata: Agriolimacidae) American Malacological Bulletin, 23, 137-156
Benke M, Reise H, Montagne-Wajer K, & Koene JM (2010). Cutaneous application of an accessory-gland secretion after sperm exchange in a terrestrial slug (Mollusca: Pulmonata). Zoology (Jena, Germany), 113 (2), 118-24 PMID: 20202803

Summer Hoverfly identification

2011-08-31T22:47:00.001+01:00

Late summer brings out masses of hoverflies in the garden. They buzz around the fennel and the wild rocket and the red valerian. Despite their superficial similarity - many are stripy yellow and black - there are 276 British hoverfly species (family Syrphidae). With a little attention to detail, though, and armed with a good identification guide (I use British Hoverflies, by Steven Falk) it is relatively easy to identify them, although there are several species complexes hard to ID to species level. The following nine species are amongst the most common in gardens in July and August. On the top photo, the, by far commonest, Episyrphus balteatus, the marmalade fly, hovering. This is a very distinctive species, due to its double abdominal dark bands. Individuals can occur in large aggregations, and are found in groups on dandelion flowers.

Sphaerophoria sp. a male on Erysimum

Female Sphaerophoria sp. on fennel.

Scaeva pyrastri, female hovering and Red Valerian

another Scaeva pyrastri on wild rocket

Syrphus on Large Bindweed. This is another very common species.

Female syrphus on Erysimum

Platycheirus scutatus on Japanese Anemone

Myathropa florea sunbathing.

The tiny Syritta pipiens, with distinctive swollen back femurs, on Nipplewort

Eupeodes luniger hovering on Herb Robert

The dronefly Eristalis tenax feeding on Lavender

An impressive slug

2011-08-27T22:25:00.004+01:00

A showery day, I come across this enormous Arion slug crossing the garden path. It must be close to 15 cm. Identification to species level is difficult to impossible as they are distinguishable by examination of internal genitalia characters - or molecular genetic analysis, and hybrids are common. British large Arion slugs are made of several species complexes, Arion ater/rufus A. lusitanicus and A. flagellus. Both groups are very polymorphic slugs, from almost white to black, including all shades of brown yellow red and orange. I have never found the the black morph in the garden, but a good representation of the others abound. The polymorphism of these slugs in the U.K., not only in colour, but also in genital characters, might stem from common hybridisation between several subspecies that colonised the British Isles from Europe, postglacially but also in more recent human introductions. Distribution changes might also come about due to expansions as a result of climate change. In addition, the slugs - except for A. flagellus - are able to self-fertilise and form relatively homogeneous populations, which might give the impression of being a separate species.

Arion slugs had deep tubercles on their backs, and no keel. At the end tip is the mucus gland, producing an extremely sticky mucus. Unlike the yellow slug, which is strictly nocturnal, Arion slugs are active all around the day, provided that it is damp. When disturbed they show a characteristic behaviour: they contract their bodies into an almost round shape and retract their tentacles inside their mantle. Inspired by a post in Myrmecos, I set the photo vertically. I had to use a white plate - instead of bowl - and allow the slug to relax and start to crawl out.

A very yellow specimen

A disturbed Arion

A selection of colours found in the garden

The black morph of Arion sp.

References

Noble, L. R. Jones, C. S. (1996). A molecular and ecological investigation of the large arionid slugs of North-West Europe: the potential for new pests The ecology of agricultural pests: biochemical approaches Ed. William O. C. Symondson, Systematics Association, special volume. Clarendon Press., 53, 93-132
Evans, N. (1986). An investigation of the status of the terrestrial slugs Arion ater ater (L.) and Arion ater rufus (L.) (Mollusca, Gastropoda, Pulmonata) in Britain Zoologica Scripta, 15 (4), 313-322 DOI: 10.1111/j.1463-6409.1986.tb00232.x
UPDATE 30/08/11: reference added and Arion ater in a photo caption changed to Arion sp.

A new adult generation of Woundwort shieldbugs

2011-08-25T16:55:00.000+01:00

Every day I check the Lambs ears for the Woundwort (or Bronze) shieldbugs, Eysarcoris venustissimus. They are usually immobile and once you've found them once, they are easy to find, although they will hide under the leaves if they feel threatened. They form clusters on the tips of leaves, not only of the Lambs ears, but also on the Enchanter's nightshade, which covers the ground on this side of the garden. Today I spotted the first adults of the year, four of them, one on a cluster of final instar nymphs; another, still white (above), looked like it had just moulted into adulthood.

A new and shiny adult Woundwort shieldbug adult on Lamb's ears

A fresh adult with three final instar nymphs

These are some nymphs on the seed stalks of Hedge Woundwort: their colours make them almost invisible at a distance, as the stalks also have a contrasting green/black pattern.

Swift hoverfly settled down for the night

2011-08-24T23:21:00.001+01:00

This hoverfly species, Scaeva pyrastri, is a challenging photographic subject. I find it particularly flighty, and many a time I have chased it across the garden as it fed on Verbena bonairensis, Buddleia, Hebe or Red Valerian. It is very aware of shapes approaching, and it cunningly and swiftly flies out of range. You really have to stalk it for close ups. S. pyrastri is a migrant hoverfly which flies from the continent to rear a generation in northern Europe and all my records are of July and August, of single individuals. Their numbers vary greatly from year to year. It is a large, handsome hoverfly, males giving the impression of having a disproportionately larze head (as above) due to their enormous eyes, which are distinctively hairy, and like in other hoverflies meet on top of their heads. The species has very characteristic white markings in the black abdomen. Adults are found in a range of flowers, while the larvae feeds on ground aphids. This male had chosen to settle in the startlingly red rowan berries and it allowed me to approach to the minimum focusing distance of my camera.

Loving the fruit

2011-08-24T17:54:00.001+01:00

Our apple and plum trees fruit in August, and there are many bugs that love them, some quite surprisingly. Slugs, springtails, woodlice and fruit flies gorge on fallen apples, and comma and speckled wood butterflies feed on blackberries, but recently I noticed a few new characters in our produce. Seven spot ladybirds clustered on overripe plums (we were away and failed to collect them) and honeybees and wasps joined them. The common wasp (Vespula vulgaris) above, kept coming back to feed on a damaged spot on this fallen apple. Sweet, sweet fruit!

7 spot ladybirds and a wasp

honeybee in plum

Bath spider hybridization

2011-08-23T22:42:00.002+01:00

Since the end of July, large spiders with long legs have been running across carpets in the house, or falling in the bath. Being fast spiders that often react to disturbance by jumping and running very fast - as opposed to crouching or playing dead - these are spiders that tend to scare people. They are males of several species of the genus Tegenaria. This guy fell in my bath a couple of nights ago and it has been the most compliant Tegenaria I've had so far. He sat still on the white bowl while I got close to its palps, but despite getting good views, I still was unable to ID it.

The two most common species in the UK are Tegenaria gigantea (=duellica) and T. saeva, and this male's palps could have been either. These closely related species differ in details of the female genitalia and of the morphology of the male palps, but their recent history is blurring the distinction between them in the north of England. Work by Peter Croucher, Geoff Oxford, and colleagues from the University of York Both spider species expanded north after the glaciations from refugia in the Iberian Peninsula. Through the vagaries of the colonisation process until recently, they had a mainly segregated distribution in the UK, with T. gigantea in the east of the country and T. saeva in the west.

Distribution in England and Wales of Tegenaria saeva and T. gigantea based on 10x10 km grid squares of standard maps (Ordnance Survey, the national mapping agency of Great Britain). Black squares, T. saeva; white squares, T. gigantea; grey squares, those containing both species. Spiders with intermediate morphologies are not included (figure from Croucher et al 2007).

In the south of the country, both species distributions meet in a narrow stable zone, in Dorset, where hybridisation appears not to be very common and when it happens results in high hybrid mortality. Since the 1970s, however, both species have expanded into Yorkshire and in this region both species often occur in the same places and hybridise commonly, so that their species boundaries are falling apart and many morphologically intermediate forms are found. As Hull is in an area of high hybridisation, although my inability to ID the spider might have more to do with my limitations, there is a high chance there is no "pure" T. gigantea and T. saeva in this area any more and that these house spiders are actually merging into one as they carry on colonising towards the north.

References
Croucher, P., Oxford, G., & Searle, J. (2004). Mitochondrial differentiation, introgression and phylogeny of species in the Tegenaria atrica group (Araneae: Agelenidae) Biological Journal of the Linnean Society, 81 (1), 79-89 DOI: 10.1111/j.1095-8312.2004.00280.x
Croucher, P., Jones, R., Searle, J., & Oxford, G. (2007). CONTRASTING PATTERNS OF HYBRIDIZATION IN LARGE HOUSE SPIDERS (TEGENARIA ATRICA GROUP, AGELENIDAE) Evolution, 61 (7), 1622-1640 DOI: 10.1111/j.1558-5646.2007.00146.x

German wasp hunting a garden spider

2011-08-19T20:36:00.004+01:00

Garden spiders have been quite obvious in the garden for a few weeks now, sitting in the middle of their webs waiting for flying insects to get entangled in their sticky threads. Garden spiders are preyed upon by other animals, including wasps - which later in the year, when garden spiders are larger and more powerful, will eat them in return. This German Wasp (Vespula germanica) caught a middle size garden spider, I saw it fly with it and settle on a drain pipe to subdue it. If the wasp stung the spider I do not know, but its abdomen was curled underneath. After giving the spider a good chew and positioning it under its legs, the wasp flew away. Wasps hunt -and scavenge, famously at picnics - to feed their larvae.

The wasp with its prey just before flying away

A large garden spider with a wasp prey in October 2008

UPDATE 24/08/11: corrected the title, which said common wasp.

Courting spiders

2011-08-19T16:53:00.000+01:00

I have posted on this common garden species, Linyphia triangularis courtship before, but I had the chance of observing this pair of spiders courting in the garden yesterday and take some phots. The male is larger, reddish and with an elongated abdomen and very large chelicerae. The female, at the back, has a rounded abdomen with a black and white pattern. As you can see in the bottom photo, there is a recent moult hanging from the web - I presume is female's, as I cannot see the large chelicers of the male. In this species the male does a form of mate guarding, sharing the female's web to wait until she has moulted and therefore she is ready for mating, and fending other approaching males off. The male vibrated its pedipalps and abdomen and slowly approached the female.

Lesser Marsh Grasshoppers

2011-08-18T18:23:00.000+01:00

Our back garden opens to an access road, on it there is an area of south facing rough ground which used to be concreted over. With time, grass has taken hold and now it is a little wild area. I cut the grass once a year trying to promote a meadow, and have sown wildflower seeds and naturalised Birds Foot trefoil, oxeye daisies and foxgloves. Today we had a big surprise when in a matter of minutes we came across two species of grasshoppers there, the first time we come across grasshoppers there. We came across at least two female Lesser Marsh Grasshopper, Chorthippus albomarginatus, a green one and a brown one, and a calling male Field Grasshopper, Chorthippus brunneus. Both are common species in the U.K. and are present in the nearby wildlife garden. I anticipate interesting grasshopper behaviour watching! watch this space for more grasshopper posts.

Lambs ears shieldbugs

2011-08-15T20:45:00.002+01:00

Although I keep Lambs ears (Stachys byzantina) in the garden for the benefit of the Wool Carder bees this plant also attracts many other bugs. They provide a lot of structure with their large woolly leaves, and spiders, harvestmen and ladybirds are often found on them. They also offer sheltered hibernation opportunities. My other favourite lambs ears bug is a true bug, the pretty shieldbug Eysarcoris venustissimus, also known as the Woundwort shieldbug, as their usual feeding plant is the native Hedge Woundwort (Stachys sylvatica). This is a small shiny bug that appears in a single generation per year. The adults are bronze, grey and white with fine black speckling. They emerge from hibernation in April and can be found mating on May. Females lay their eggs in Stachys plants. Nymphs can be easily found on July and August and by September there is a new adult generation. Today, I watched at least nine nymphs in various stages of development on the Stachys plant. Nymphs are green and black or pinkish and black. All the nymph photos were taken today.

An early instar nymph. The object near it are seeds of Circaea luthethiana

A group of Wounwort shieldbugs with a green shieldbug nymph.

A last instar nymph. They can be recognised by their black wing buds

A mating pair on Stachys bizantina (11/5/11)

UPDATE 25/08/11. Replaced a photo with the early instar one.

Bright brimstone

2011-07-27T21:58:00.002+01:00

The sun came out in the afternoon after a grey start, so I went again to my local wildlife garden for a Big Butterfly Count. Although I was disappointed not to see Ringlets or Gatekeepers, the fact that I found the Brown Argus again - this time two individuals - and this fresh male Brimstone made up for it big time. Brimstones, Gonepteryx rhamni, are beautiful, but frustrating butterflies. In the last three years I've seen 13 individuals, and until today, I had only managed to get very distant shots of two of them, the rest flew and flew non stop. The Brimstone hibernates as an adult and is a long lived butterfly. The adults emerge at the end of July or early August, and they can live up to 10 months. Compared this with the few weeks (4 days on average) that Brown Argus can live.
This male Brimstone fed on Hemp Agrimony for quite a while, and then moved on to buddleias. It was so content feeding that I could get very close for shots. Brimstones have long tongues and they can feed even on Teasels, which have very deep corolas. While in flight, the Brimstone is very visible, but once it lands, its yellow-green colour and the asymmetric dots on its wings give it has a fantastic camouflage, appearing to be a droopy, yellowing leaf.

The Big Butterfly Count. There is time until the 7th of August if you haven't done one. You only need 15 minutes in a sunny spell.

The little Brown Argus complex tale of range expansion

2011-07-27T20:21:00.002+01:00

Climate change is making a measurable impact on the distribution of many organisms. The populations of some species are disapearing or becoming more fragmented, increasing extinction risk, others are actually expanding their range north with the increasing temperatures. Insects - and particularly butterflies - are very sensitive to changes in climate, and amongst the winners of climate change is a lovely, tiny butterfly, the Brown Argus, Aricia agestis. In the last few days, I have spotted this butterfly in two new locations in East Yorkshire, including my local wildlife garden, where it is unlikely I would have overlooked it, indicating recent colonisation.

Distribution of Brown Argus (Aricia agestis) in Britain. Black circles show that the species was present in 1970–1982; open circles show newly colonised areas (1995–1999 records, not present in 1970–1982). Circles represent 10 km grid cells (from Menéndez et al 2008)

This species has increased markedly in range in the U.K in the last 30 years, expanding around 10 km per year since the early 1990s, reverting a previously declining trend. This could be seen as a direct response to climate change. But the story is not that simple, the positive response to temperature has been facilitated by changes in the interactions of this butterfly with other organisms. Before the expansion, the predominant caterpillar foodplant of the Brown Argus was the Common Rock Rose, Helianthemum nummularium, a plant that grows on sheltered, south facing, sunny hillsides in chalk and limestone grasslands. Some southern populations used several species from the geranium family, especially Geranium and Erodium. These plants grow on lowland, in cooler habitats than the Rock Rose, so only after temperature increased were these populations able to colonise and exploit these areas. Chris Thomas and collaborators established that expanding populations had a preference to lay their eggs on the more available geraniums, even when they came from populations in hills using Rock Roses. This diet/habitat shift allowed the butterfly to recolonise distant Rock Rose areas, using lowland geranium habitat as stepping stones, which single dispersing butterflies would have been unlikely to reach. A niche model - based on preferred temperature and established food plant - of the predicted range expansion would have grossly underestimated the recent expansion of this butterfly.
A further complexity stems from an "enemy release" effect. Invasive populations - often translocated by man from distant areas - are hypothesized to expand unchecked as they have left behind their natural enemies: specialist predators, parasites or parasitoids might be absent, and generalist ones might not have the right "search image" for them. Rosa Menéndez and her collaborators tested if this applied to an expanding native population, where the distance travelled from the nearest population is smaller, and there are related species whose parasites might also infect them. They used the Brown Argus and its parasitoids as models. The Brown Argus shares its range with a very common and related species, the Common Blue, Polyommatus icarus, and four parasitoids use both species as host, therefore there is potential for the parasitoids to use the expanding butterfly. They compared the rates of parasitism of old established populations and newly colonised populations. Although both were parasitised by a similar number of parasitoid species (old, six parasite species, new, five), the new Brown Argus populations had an overall lower parasitism rate than the established ones.

Population

Observed parasitism (%) of Aricia agestis caterpillars (i.e. sum of parasitism by

all parasitoid species) during the first generation in 2004 populations that differ in the

position within the butterfly range (established vs. new parts of the range). Values are mean + SE and numbers within bars show sample sizes (numbers of caterpillars collected) (from Menéndez et al 2008)

The northward expansion of the Brown Argus is therefore not a direct response to temperature, but the result of a complex interaction including both a diet shift and a partial release of their parasites. This complexity of the biological interactions of each species makes it even more challenging to predict the responses of species to climate change.

References
MENÉNDEZ, R., GONZÁLEZ-MEGÍAS, A., LEWIS, O., SHAW, M., & THOMAS, C. (2008). Escape from natural enemies during climate-driven range expansion: a case study Ecological Entomology, 33 (3), 413-421 DOI: 10.1111/j.1365-2311.2008.00985.x
Thomas CD, Bodsworth EJ, Wilson RJ, Simmons AD, Davies ZG, Musche M, & Conradt L (2001). Ecological and evolutionary processes at expanding range margins. Nature, 411 (6837), 577-81 PMID: 11385570

Bug babies leave their siblings

2011-07-26T18:09:00.001+01:00

After at least ten days clustering together on top of their egg cases, the 28 Green Shield Bugs, Palomena prasina, nymphs finally left their siblings after moulting into a greener instar. This is the sequence of events:

12/7/11

13/07/11

20/07/11 All have now moulted into the greener 2nd instar

22/07/11. The nymphs start to disperse in the morning.

22/07/11. After an hour, only three reluctant nymphs remain on the egg cases. In the evening they had all dispersed.

Some of the adventurous nymphs. I found one a meter away from the egg cases.

Parasitic wasps turn ladybirds into their bodyguards

2011-07-23T18:33:00.002+01:00

I have covered the ladybird parasitoid Dinocampus coccinellae before. Some recent research, however, has uncovered some fascinating aspects of this little wasp's manipulation of its host behaviour. The parasitoid wasp, below, injects a single egg on a ladybird using its ovipositor (visible in the top photo of a just emerged D. coccinellae).

After hatching, the larva feeds on its host internal organs, and after about 20 days, she emerges from the ventral plates of the ladybird to pupate. She spins a cocoon that tethers the ladybird to the substrate (top photo) and pupates inside. Unlike many parasitoids, Dinocampus does not kill its host. But the ladybird cannot escape, not only she is tethered, in addition, before emerging from the ladybird's body, the larva is thought to produced some chemicals that affect the ladybird's brain and compels it to sit still, and to twitch when disturbed. The parasitized ladybird colours and twitching were through to afford the parasitoid some protection from predators while in the cocoon. Fanny Maure and her collaborators provided the much needed evidence for this hypothesis in some laboratory experiments. They infected ladybirds - Coleomegilla maculata, a Canadian species - with Dinocampus coccinellae, and once the cocoons were spun under the ladybirds, they split the coccoons into three groups. In the first group of cocoons, they removed the ladybird, in the second, they killed the ladybird and in the third they left the ladybird untouched in the usual position on top of the cocoon. Then they exposed their cocoons to a predator, third instar green lacewing larvae Chrysoperla carnea and counted how many cocoons were predated in each group.

Percentage of Dinocampus coccinellae cocoons eaten by larval green lacewing, Chrysoperla carnea, when parasitoid cocoons were exposed alone, covered by a dead ladybird (Coleomegilla maculata), or attended by a living ladybird. Probabilities were obtained using the Fisher exact test, ***p , 0.0001. Numbers refer to sample sizes (from Maure et al 2011).

Parasitoid cocoons alone or sheltered with a dead ladybird suffered significantly more predation by lacewing larvae that did those protected by living ladybirds, supporting the hypothesis that the parasitoids manipulate the ladybird's behaviour to their own advantage, effectively converting them into their own bodyguards. The ladybird protective colours made little difference, although these are thought to protect against bird, not insect, predators.

Presumably, there must be a cost to the larvae to manipulate the ladybird. She must left the ladybird alive and produce chemicals to make it into her bodyguard. Maure and coworkers also tested this, by measuring the relationship between the ladybird lifespan once the parasite emerged and the survival and fecundity of the parasite. Their results show a significant negative correlation between the ladybird lifespan - 25% survived the parasitoid emergence - and the number of mature eggs the parasitoids had in their bodies after emergence as adults. This suggest that indeed there is a cost to making your host into a bodyguard. Overall, though, it must compensate the parasite to shield itself with the live ladybird in terms of predator avoidance.

Reference

Maure F, Brodeur J, Ponlet N, Doyon J, Firlej A, Elguero E, & Thomas F (2011). The cost of a bodyguard. Biology letters PMID: 21697162

Shelter and food for a cold leafcutter

2011-07-22T21:09:00.003+01:00

I pity the leaf-cutter bees on cold or wet days. They really are sun-loving bees and when the weather is not to their liking they hide in the bee hotel, peeking out of the holes, hoping for the sun to appear. I found this cold male Megachile willughbiella clinging to a hardy geranium flower after a shower a few days ago. Geraniums are one of their favourite flowers, and they also makes a handy umbrella.

Sexing Lesser Stag Beetles

2011-07-21T22:37:00.001+01:00

There appears to be a healthy Lesser Stag beetle population in the neighbourhood. Only in my street, I have come across at least six individuals (unfortunately, two of them had been squished on the pavement) in four years. So far, however, I had only seen females, and I was pleased to find a fierce-looking male this morning. This species is often mistaken with Stag Beetles. But Lesser stag beetles are smaller and uniformly black-grey with fine puntuated bodies. They have strong legs with teeth which they use for digging, especially the females, and, when disturbed, they crouch and retract their legs and antennae under their bodies. Although they are not as easy to sex as the Stag Beetle, males and female Lesser Stat Beetles can be told apart based on several features. First, males have larger mandibles, with a rounded knob on them. Females have two characteristic small bumps on their forehead, between their eyes. The third one is that male heads are wider, almost as wide as their thorax, and therefore their mandibles are also set wider apart. Based on the photos and info I've seen, it appears to be a lot of variation on body size (from 20 to 32 mm) and in knob size in males.

Male

Female

For lots of information about the life cycle of the Lesser Stag Beetle and relatives visit Maria Fremlin's website.

Ants tending aphids

2011-07-21T20:47:00.002+01:00

Ants have a sweet tooth. They gather nectar from flowers, buds and nectaries but also farm animals to obtain their sweet honeydew. These farmed animals are scale insects and aphids. Ants tend the aphids (above), protect them from their predators and parasites and keep them together for easy "milking". To obtain the honeydew produced by aphids, ants stimulate them with their antennae, after which the aphid will secrete a droplet of sugar rich liquid. These ants are tending groups of aphids on an Iris leaf. To soften the built-in flash light I put a piece of kitchen paper in front of it, holding it with my left finger.

Small white or small ultraviolet butterfly?

2011-07-19T23:00:00.000+01:00

Graced with a few black spots and a shade of yellow in their underwings, the plain wings of white butterflies contrast with the colourful and rich patterns of other butterflies. Unfortunately, this is a reflection of the limitations of our visual system. Male and female Small White butterflies, Pieris rapae, have different upper wing colours, especially in the ultraviolet (UV) spectrum: males absorb UV strongly but reflect most visible light, so they look a brighter white than females to us, but have a dark tone in the UV spectrum, which we cannot see.

A Small White bilateral gynandromorph, with visible female coloration on the left and male coloration on the right (top). Below, a false-colored representation of how these wing colors might be perceived by small whites, which are able to see UV light (photo courtesy of Nathan Morehouse)

Wing colour patterns in pierid butterflies, the family of the Small White, depend on beads made up of pigments called pterins, which are deposited on wing scales, and in the Small White are UV-absorbing. Males vary widely in their brightness and UV reflectance. Males able to produce more beads have darker UV patterns and appear brighter to our eyes. The amount of pterins a male can produce depend of the diet they had as caterpillars. Pterins need a lot of nitrogen to produce - they are the most nitrogen-rich pigment in animals - and the caterpillars can be nitrogen limited, so a brighter male is an indication of a good caterpillar diet. A brighter male also is also expected to be more desirable to a female, as during mating, male white butterflies transfer nutrients to the females in the form of infertile sperm, a nuptial gift which will increase the females life expectancy and therefore will be able to lay more eggs. A male with a higher quality diet can afford to be brighter and to produce bigger and more nutritious nuptial gifts.
These butterflies are also able to see UV patterns, they have a rich repertoire of visual receptors in the short wavelength, including three types of photoreceptors that peak at UV, violet and blue. Crucially, being aware of their ability both to emit and detect UV allows us to understand their mating behaviour. Nathan Morehouse and Ronald Rutowski carried out some elegant experiments to test the hypothesis that females choose males with more contrasting UV patterns. They carried out two experiments, in both of them they used lab-reared virgin females, which they presented with some males in a large cage. In the first experiment they used males that were from wild origin, and therefore had a natural range of colour patterns, in the second experiment they used laboratory reared males, but dipped the males' wings in a chemical that partially removes the beads, this way they created a range of variation that mimicked the natural one, but removing other possible confounding effects such as age, nutritional state, effects of encounters with predators or mating history. They removed the mated males to carry out measurements and they allow each female to mate three times. Then they also measured males that hadn't been mated. Females are able to exercise mate choice as they can adopt the "mate refusal posture" by which they lower their wings and raise their abdomen as shown in the photo below when they don't want to mate. Males showcase their wings during their ritualised courtship flight

Courting Small White butterflies. The female, underneath the male is rejecting him by lifting her abdomen and lowering her wings.

Their experimental results (below) together with further modeling of the female's visual system indicated that females, as expected, prefer to mate with brighter males. Sexual selection therefore favours brigher males.

Spectral reflectance of male and female Pieris rapae in study 1 (A) and study 2 (B). Average female phenotype (dashed lines), average mated male phenotype (solid lines), average unmated male phenotype (dashed and dotted lines), and minimum and maximum male values (dotted lines) are displayed. Histograms to the right are for all males, with the proportion of mated males (solid region) and unmated males (open region) indicated in each bin (from Morehouse & Rutowski 2010).

However, not everything is rosy (or ultraviolet if you wish) for these males, as the same colour patterns that make males more attractive to females, make them more visible to their main predators, birds, which are also able to see in the UV range. This study shows how sexual selection and natural selection through predators can work in an opposite direction, and reminds us that beauty is in the eye of the beholder.

References

Morehouse NI, & Rutowski RL (2010). In the eyes of the beholders: Female choice and avian predation risk associated with an exaggerated male butterfly color. The American naturalist, 176 (6), 768-84 PMID: 20942644

Mating buff-tailed bumblebees

2011-07-19T22:22:00.004+01:00

Next to a busy road, by the base of a tree, surrounded by concrete and oblivious to the noisy traffic, this pair of White-tailed bumblebees were mating this morning. The queen lying motionless, a bit sideways, the male tickling her rhythmically with his legs. I have been taking some videos with my camera lately to record some unusual, or more common bug behaviour. I hope this works as it is the first time I upload a video to BugBlog.

* * *

I wrote the piece above almost 5 months ago, on the 19th of July, when I saw the bumblebees mating. I tried, and miserably failed to upload a video to YouTube. Here it is, finally posted. Thank you Crystal Ernst! More to come.

Birds and ant swarms

2011-07-16T22:10:00.000+01:00

In July and August, typically in sunny days after rains, swarms of reproductive Black Garden Ants (Lasius niger) - winged queens and males - emerge from their nest to mate and start new colonies. Workers also come out en masse and run around the entrance of the nest, looking agitated. I had often noticed this and wondered why do workers did this, until yesterday, watching a Blackbird feeding on the winged ants coming out of their nests, realised why. The Blackbird run close to the entrance, fetched a winged ant and run away. The bird repeated this several times and was obviously being stung or sprayed by the ants around the nest, but still wanted to feed and its back-and-fro behaviour was evidence of the - at least partial - success of the frantic workers keeping predators at bay. Winged ant have many predators. Some casually feeding on the winged ones, others opportunistically making use of a plentiful, although ephemeral, bonanza. A range of birds fall in the latter category, starlings and sparrows feed on the winged ants - sometimes using fly-catcher techniques - and seagulls have been seen feeding on them up in the sky. While reading a paper on this, I remembered that last year, on the day the ants emerged, I looked up in the sky and saw many small flying things and thought they might be the flying ants. When I looked more closely I saw they were seagulls, and was surprised at how many there were, well over a hundred, soaring very high up. I took a shot (below) and forgot about it. They were most likely feeding on the winged ants that had been carried high by thermals in their swarming mating flight.

Seagull flock feeding on swarming ants (26/07/10)

This is the nest in the bottom right hand corner of the top photo

Workers around a nest with winged ants emerging (26/07/10)

Reference

James Baird and Andrew J. Meyerriecks (1965). Birds Feeding on an Ant Mating Swarm. The Wilson Bulletin, 77 (1), 89-91.
Gilbert S. Grant (1992) Opportunistic Foraging on Swarming Ants by Gulls, Shorebirds, and Grackles. The Chat, 56, 80-82.

A celebration of butterflies

2011-07-15T20:32:00.000+01:00

I have gone through my files and made a selection of common butterflies to celebrate these beautiful insects in anticipation of the Big Butterfly Count, that starts tomorrow (16th to 31st of July) . This year it will last two weeks so there is more chances you can be out during good butterfly weather. You need to count what butterflies - and moths - you see in 15 minutes during a sunny spell. You can complete as many surveys as you want - from different days or different places - and you have time until the end of August to submit your records online. Click in the photo to start the slideshow.

Poisonous bug babies cluster together

2011-07-14T21:41:00.001+01:00

These newborn green shieldbugs, Palomena prasina, look most unlike adults. They have a bright black-red warning colouration in their first instar, for a few days they cluster tightly together on top of their egg shells. After moulting into their second instar they change colour to green and black and they disperse away from their siblings. All shieldbugs, including nymphs have stink glands between the first and second pair of legs. If handled roughly they can release repellent chemicals and they are often brightly marked. But why do these bugs cluster together?
The contrasting black and yellow or black and red patterns of Cinnabar moths, ladybirds, Burnet moths, bumblebees and wasps are visual signals to potential predators indicating that the animal is distasteful, poisonous or dangerous in some way. The predator, having had a nasty encounter with the aposematic organism learns to avoid it. But how does does aposematism evolve in the first place? You would think that the first aposematic individual either dies or is injured in the process, so it cannot be though natural selection, right? One possibility, first suggested by Sir Ronald Fisher in 1958 is aggregation of related aposematic organisms:

For, although with the adult insect the effect of increased distastefulness upon the actions of the predator will be merely to make that individual predator avoid all members of the persecuted species, and so, unless the individual attacked possibly survives, to confer no advantage upon its genotype, with gregarious larvae the effect will certainly be to give the increased protection especially to one particular group of larvae, probably brothers and sisters of the individual attacked. The selective potency of the avoidance of brothers will of course be only half as great as if the individual itself were protected; against this is to be set the fact that it applies to the whole of a possibly numerous brood

Fisher's hypothesis of kin selected aposematism has been questioned recently. Although aposematic organisms tend to be gregarious, phylogenetic analysis suggest that aposematism evolved before gregariousness, so aposematism makes gregariousness easier to evolve, and not the other way round.
Birgitta Sillen-Tullberg carried out some elegant experiments showing that aposematism can give direct benefits to the individual, and that kin selection is unnecessary. She presented hand reared Great Tits (Parus major) with two colour forms of the same bug species (Lygaeus equestris), one grey and black (cryptic), and the other - the common form- red and black (aposematic). A group of tits was presented with cryptic prey and another group with aposematic prey in 11 trials per bird. Great Tits learned to avoid both cryptic and aposematic prey - remember both are equally distasteful - but attacked cryptic prey more readily from the first trial.

In addition, when attacked, aposematic prey survived more, indicating that the tits were more wary when attacking it.
Being grouped, though, can confer further advantages. Gabriella Gamberale and Birgitta Tullberg carried out experiments testing the effect of grouped versus solitary prey - bugs, Spilostethus pandurus - on learning avoidance by predators - chicks in their experiments. Chicks learn to avoid aposematic shieldbugs in fewer predation attempts, and were less likely to attack twice they are aggregated than if the prey is solitary. They concluded that gregarious aposematic prey are a more effective signal for the chicks to learn, the reasons why this could be are still unclear.

References
Fisher, Ronald A. (1958). The Genetical Theory of Natural Selection Dover Publications, Inc. Other: 0-486-60466-7
Sillen-Tullberg, B. (1985). Higher survival of an aposematic than of a cryptic form of a distasteful bug. Oecologia, 67 (3), 411-415 DOI: 10.1007/BF00384948
Gamberale, Gabriella, & Tullberg, Birgitta S. (1996). Evidence for a more effective signal in aggregated aposematic prey. Animal Behaviour, 52 (3), 597-601 DOI: 10.1006/anbe.1996.0200

Face off

2011-07-12T20:55:00.001+01:00

Ectemnius wasps are skilled fly hunters. Not only they hunt flies, but some species specialise in hoverflies, those masters of controlled flight. Like their prey, Ectemnius wasps are able to hover. As their large eyes suggest, they hunt visually and inspect flower patches that hoverflies frequent, hovering a bit, changing body direction, inspecting their terrain thoroughly. Once they detect a hoverfly, they try to approach from behind, and when at about 10 cm they aim and attack. Ectemnius provisions its nest - dug in dead wood - with hoverflies, which will serve as food for its larvae. The adults themselves feed on nectar. I was trying to photograph this digger wasp stalking hover flies, when it came across a male Syritta pipiens. The tiny hoverfly male, which often confronts other hoverfly males on this patch of wild rocket, instead of fleeing, it confronted the wasp, mirroring the predator movements and keeping his distance, both insects hovering perfectly still in front of each other for a few moments. Surprisingly, the wasp did not attack the fly and just moved on. Some insects have been shown to display a stealth strategy called "motion camouflage" by which an individual (the shadower) can conceal its movements to another individual (the shadowee) by maintaning its position in the retina of the shadowee. The shadower then appears as an stationary object from the point of vision of the shadowee. Some male hoverflies (and Syritta pipiens in particular) use this flying strategy to track females undetected and dragonflies use it to avoid being detected when intruding in other territories and it is also suspected to be used by visual insects when approaching prey. A range of models have been developed to simulate this strategy. Unsurprisingly, engineers are developing motion camouflage strategies to be applied to robots, satellites or with military purposes.
According to Justh & Krishnaprasad:

Motion camouflage can be used by a predator to stealthily pursue the prey, but a motion-camouflage strategy can also be used by the prey to evade a predator. The only difference between the strategy of the predator and the strategy of the evader is that the predator seeks to approach the prey while maintaining motion camouflage, whereas the evader seeks to move away from the predator while maintaining motion camouflage.

I wonder if this was the case in the above photo. A temporary stale mate, but the prey got away.

References
Justh, E., & Krishnaprasad, P. (2006). Steering laws for motion camouflage Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 462 (2076), 3629-3643 DOI: 10.1098/rspa.2006.1742

Mizutani, A., Chahl, J., & Srinivasan, M. (2003). Insect behaviour: Motion camouflage in dragonflies. Nature, 423 (6940), 604-604 DOI: 10.1038/423604a

Fresh Holly blue shows its tongue

2011-07-11T21:17:00.000+01:00

July is peak time for butterflies. What up to mid June seemed like a poor butterfly year is gearing up to a great one. Just today I watched 8 species locally. The most striking of them was this freshly emerged Holly Blue male. It is the first individual of the second generation I see this year. It basked in the morning sun in a front garden, and - unusually for this species - it sat with wings fully open for a while. Once warm, the butterfly closed its wings and fluttered onto another perch and stretched its tongue.

A more usual sitting posture for a Holly Blue, with closed wings

The butterfly with its short tongue stretched

Tongue length in butterflies is correlated with body length, so it is not surprising Lycaenids, the family to which the Holly Blue belongs, being small butterflies, have short tongues, around 8 mm. Whites and Brimstone and the Nymphalids have longer tongues, around 15 mm. For their length, some moths (such as the Hummingbird Hawkmoth) have very long tongues, 28 mm. The following table from Pollination and Floral Ecology by Pat Willmer illustrates the length differences between some butterflies and moths.

Tongue length determines the maximum depth of a flower corolla that a butterfly can take nectar from. Short tongued species prefer shallow flowers, often composite ones like brambles, tansy, hemp agrimony or dandelions.

Emerging harlequin ladybird

2011-07-09T19:36:00.000+01:00

I collected 50 ladybird pupae (above) a couple of weeks ago. The idea was to wait and see what emerged from them to send records to the Ladybird Parasite Survey. After 6 days, 46 Harlequins had emerged, and from 2 of the remaining some tiny maggots of the parasitic phorid fly Phalacrotophora. Having so many ladybirds emerging at home meant I had a good chance to catch one of them emerging, something I had never seen before. I saw two, one of them almost right from the beginning, and this series of photos documents it. The whole process took about 10 minutes. In the next shot, the ladybird has broken the pupal skin and the pupal buds containing both pairs of wings are erect.

...she finally walks out.

The ladybird then waits next to its pupal skin until she has hardened a bit and extends her wings, which are still yellow. You can see how the ladybird gets her spots in this post.

Darting Small skippers

2011-07-08T18:34:00.001+01:00

A grassy area in the little wildlife garden near where I live is managed like a meadow, cut once a year. The grass is long and lush now, peppered with a range of wildfowers. One of the insects that benefits from this arrangement is the Small Skipper, Thymelicus sylvestris. The males of this golden brown, little butterfly dart around the meadow, stopping to feed or sunny themselves occassionally. The larval food plant of this species is Yorkshire Fog, a common rough grass. The adults emerge in mid June and fly in a single generation until August. They like to feed on clovers, bird's foot trefoil, restarrows, knapweeds, thistles, brambles and hawkbits. This is another butterfly species thought to have benefited from recent climate warming in the U.K. It now inhabits most of England and Wales, with its range having moved north about 100 km in the last 25 years.

A male, the same individual as above, resting on Bird's Foot trefoil. Male skippers can be distinguished from females by their "sex-brand", a dark like in the middle of their forewings.

Brown-Lipped Snails

2011-07-07T21:18:00.000+01:00

The Brown-lipped or Grove snail, Cepaea nemoralis has received a lot of attention by evolutionary biologists for more than a century, due to their strikingly variable shell colour - what is called colour polymorphism. In the decades of the middle of the last century it was a very popular research organism. The shiny shell can be yellow, pink or brown. Over each of these background colours there can be no bands, one band or five bands, and the bands can also be fused and be of variable width. The snail above, which we found yesterday feeding on the fallen leaves on the garden path, is a yellow/one banded one. This polymorphism happens within the same population, but what puzzled biologists was the occurrence of sharp changes in the frequency of colour forms from one population to the next, and these differences seem to persist with time. This phenomenon was called "area effects". Many explanations have been proposed through the years to explain how the polymorphism is maintained and how area effects come to be, from differential predation (especially by song thrushes), adaptation to microhabitat, or other forms of selection to chance effects due to colonization after the glaciations, genetic linkage, dispersal between populations, etc. Many of these factors are not mutually exclusive and seem to have different importance depending on the population.
We found the shells below in the beach in Spurn Head a few years ago, all in a small area. They are a bit bleached by the sun, but you can see yellow and pink snails and three types of banding patterns.

The Brown Lipped snail can be found from dunes to roadsides, gardens and closed woodland. It can live up to 8 years old. They prefer to feed on dead vegetation than fresh, and on average, only 9% of its diet is fresh vegetation, although this percentage can increase during dry spells.

References
Cain AJ, & Sheppard PM (1954). Natural Selection in Cepaea. Genetics, 39 (1), 89-116 PMID: 17247470
Davison, A., & Clarke, B. (2000). History or current selection? A molecular analysis of 'area effects' in the land snail Cepaea nemoralis Proceedings of the Royal Society B: Biological Sciences, 267 (1451), 1399-1405 DOI: 10.1098/rspb.2000.1156
Paul J. Mensink & Hugh A. L. Henry (2011). Rain event influence short-term feeding preferences in the snail Cepaea nemoralis Journal of Molluscan Studies. DOI: 10.1093/mollus/eyr011

Amber Snail Puzzle

2011-07-05T21:26:00.002+01:00

While removing an old pot containing a lot of grass and a dead Agapanthus, next to a rainwater filled pot, I stumbled upon this little snail. I was quite surprised as initially, I thought it was a pond snail, but closer inspection revealed the tell-tale eyes-on-top-of-tentacles characteristic of land snails and slugs, while aquatic snails have their eyes at the base of their tentacles. After sifting through a Molluscs guide I found out it was a Common Amber Snail, Succinea putris. Although not aquatic, it usually lives near water or in waterlogged habitats, and it is often found on the stems of aquatic plants. It cannot retract its body completely inside the shell, and the lower pair of tentacles is vestigial. I have no idea how this snail got into our garden, but snails, despite being slow and strongly dependent on humidity, are known to disperse widely. In the Origin of the Species, Charles Darwin believed birds were the most common long range dispersal agents of snails and other aquatic animals and plants. In 1893, Harry Wallis Kew reviewed the dispersal of land and water molluscs, and discusses the evidence for external transport on the feathers of birds:

Sir C. Lyell, remarking on the wide range of Succinea putris, a land-shell which inhabits moist places on the borders of pools and streams suggested that water-fowl might have distributed its ova entangled among their feathers and it seems quite likely that ova of certain terrestrial kinds may be occasionally thus carried, either in the feathers or on the feet of birds; indeed, we have a near approach to proof of such transportal, the Rev. Canon Tristram, as we have seen, having once found ova, believed to be those of a Succinea, upon one of the feet of a mallard shot by him, on the wing, in the desert of Sahara. It is doubtful, however, whether Succinea, from the nature of the localities they often or usually inhabit, ought not, for the present purpose, to be classed with fresh-water, rather than with land-shells. Mr. Darwin suggested that the just-hatched young, possibly, might sometimes crawl upon the feet of ground-roosting birds, and thus get transported; and it certainly seems in the highest degree probable that such is the case, but, as far as I know, no observations in support of such a supposition have yet been made.

A tantalizing possibility, also first put by Darwin, is that of internal transport of organisms in the digestive tract of birds. Many bird species feed on snails, and given that no gastric juices occur in bird's crop, they can potentially survive for a while and maybe be discharged later elsewhere by the bird, or regurgitated by raptor if the bird falls prey to it. Kew stated:

Twenty specimens of a Succinea, peculiarly packed together, and four of Pupa viuscornvi were once found by Mr. W. H. Dikes in the crop of a bearded titmouse (Parus biarmicus); all the shells, it is said, were uninjured, but it is not stated that any were observed lo be alive.

In 1968, Biggs reported on the recovery of a living Succinea putris from a pigeon's crop at least 8 h after the bird had died. Indeed, although it seems even more unlikely, some snails can survive passage through the whole digestive tract of birds provided the shell is more or less unbroken. This has recently been shown to happen to a small estuarine snail, Hydrobia ulvae, which can survive passage through the digestive tract of Shelducks, and also in some small Japanese terrestrial snails, Tornatellides boeningi a proportion of which were recovered alive in the feces of two species of terrestrial bird they had been fed to.
I don't think any of these forms of dispersal apply to the particular little snail in the above photo. Maybe it travelled on a pot plant we bought some time back in a garden centre, or, stuck to our clothes or shoes during an outing into some wetlands. Maybe, but just that any of the forms of transport Darwin and Kew discussed actually happen to snails shows you don't need wings to fly high.

References
Biggs, H. E. J. (1968). Succinea putris (L.) in a pigeon's crop Conchologist Newsletter, 24: 36.

Gerhard Cadée (2011). Hydrobia as "Jonah in the whale": shell repair after passing through the digestive tract of shelducks alive. Palaios, 26 (4), 245-249 DOI: 10.2110/palo.2010.p10-095r

Darwin, C.R. (1959) On the Origin of Species. Read the book here.
Kew, H.W. (1893) The dispersal of shells: an inquiry into the means of dispersal possessed by fresh-water and land Mollusca. K. Paul, Trench, Trübner & Co., Ltd. Read the book here.
Shinichiro Wada, Kazuto Kawakami and Satoshi Chiba (2011). Snails can survive passage through a bird's digestive system. Journal of Biogeography : doi:10.1111/j.1365-2699.2011.02559.x

Six-spot burnets: chemical weapons as nuptial gifts

2011-07-03T21:37:00.003+01:00

Six-Spot Burnets, Zygaena filipendulae, are spectacular day flying moths. The contrast between their colour and the green meadows where they live makes them very obvious. Their body and forewing background are black, with a metallic green-blue sheen. Their forewings have six crimson-red spots. In addition they are large and heavy, and females like to perch conspicuously atop flower heads. You cannot miss a sitting burnet, but a flying one is even harder to miss: when they fly, a slow, buzzing, heavy flight, their crimson rear wings with a narrow black border become visible. As you could predict, this bright, black-with red spots contrasting colouration is a warning sign. Burnet moths are toxic, when they are injured, they release cyanide, a highly poisonous chemical. Cyanide compounds are found at some level in every life stage from egg to adult. The larvae sequester and store cyanogenic compounds from their food plants - Bird's Foot Trefoil, Lotus corniculatus - and all life stages are able to synthesize these chemicals themselves. However, production of the chemicals is costly, as larvae grow much more slowly when reared on varieties of Bird's Foot Trefoil lacking cyanogenic chemicals, as they have to synthesize them all themselves. There is a sudden loss of cyanogenic compounds from the last larval stage to the adult, and there also appears to be large variation in the amount of toxic chemicals in the adults. This could partly be explained by volatile hydrogen cyanide emissions by larvae - possibly as an antipredator strategy. Also, males convert some of their cyanogenic compounds into a pheromone; upon approaching a female, they release it. Females are able to determine how much pheromone a male is producing, the larger the quantity, the more likely the female is to accept him. But things get even more interesting. Mika Zagrobelny and co-workers, from the University of Copenhagen, collected Six-Spot Burnet larvae, pupa and adult from a local fallow field and made detailed measurements of the levels of cyanogenic compounds in the tissues of the different life stages, and also their toxic emissions. They found that females, as the larvae, emit hydrogen cyanide. Males are attracted to these chemical plumes, which form part of a pheromone cocktail produced by the female.

Average total cyanogenic compounds content in virgin and mated Z. filipendulae adults as well as in discarded males (which females would not mate with). Error bars are standard deviation. (figure modified from Zagrobelny et al. 2007).

The researchers then compared the cyanogenic compounds of virgin males and females, as well as mated males and females they paired up in the laboratory (see figure above). Virgin males and females had roughly similar levels of cyanogenic compounds. In contrast, after mating, females had larger levels, whereas males had lower levels. This indicates that during mating, males transfer some of these chemicals to the female, likely with the sperm. The levels of cyanogenic compounds in rejected males (males in an experimental pair that the females refused to mate with) were lower than average levels in virgin males, which suggests that females will mate preferentially with those males better loaded with chemical weapons. Why would the female benefit from acquiring more cyanide compounds. Possibly because the more she puts into eggs, the better defended they will be from predators, so this nuptial gift might be seen as a form of paternal behaviour. Alternatively, the female might gain through using this nuptial gift to produce more pheromone, attract further males and increase the vigour of her offspring.

A Six-Spot Burnet on Bird's Foot Trefoil

References
Zagrobelny M, Bak S, Olsen CE, & Møller BL (2007). Intimate roles for cyanogenic glucosides in the life cycle of Zygaena filipendulae (Lepidoptera, Zygaenidae). Insect biochemistry and molecular biology, 37 (11), 1189-97 PMID: 17916505

Leaf-cutter bee antics

2011-07-01T10:20:00.001+01:00

There has been a lot of leaf-cutter bee activity in the last week in the garden. Females collect nectar and pollen from Campanula, wild rocket (female collecting pollen above), everlasting peas, and birds foot trefoil. They have colourful pollen baskets underneath their abdomen.

Males patrol the females' favourite nectar and pollen sources. Here a male Megachile willughbiella, easily recognisable by their white-golden mittens and moustache, flies by everlasting pea flowers.

They also keep a close eye on the bee hotel, where, for the first time, I have seen nesting activity, and often bask on top of it or nearby on sunny spells.

Males of Megachile willughbiella also "sleep" in the hotel, or seek refuge during cold or rainy spells. On the photo above, two males settle for the night. The plugged nests around them belong to Osmia rufa, the red mason bee.

When they detect a female feeding, males hover in front of them for a little while before attempting mating. The following description is for Megachile fortis, an American species of leaf-cutter by John Neff and Beryl Simpson, may well apply to the british Megachile species:

When a female was encountered on a sunflower head, the male hovered in front of the capitulum while the female moved around it, probing the circular array of florets. When the female reached the 1200 position (aligned vertically on the capitulum with her head up) he darted forward and grasped her with his fore and mid legs, rapidly curling his abdomen under the tip of her abdomen, apparently attempting copulation. Both bees then dropped from the flower with the female quickly escaping or being released to fly away and resume foraging. The period from pouncing on the female to release was quite brief, typically less than 3 seconds.

Today I had the chance to observe a female Megachile willughbiella repelling a male. She was basking on top of the bee hotel and the patrolling male spotted her. He pounced on her but she curled her abdomen up as you can see in the photo above. The male flew away and the female adopted a more relaxed position. Leaf-cutter have very mobile abdomens and tend to tip them upwards. I have no idea why, but I wonder if it has something to do with their pollen collecting. However, males also have this tendency to raise their abdomens when feeding or just when preening themselves.
I have posted before on these species leaf-cutting behaviour itself, but I had never had the chance to look at a finished nest from close up. Two nests were finished in the last couple of days in the bee hotel. As you can see below, nests come in colours. I wonder if the yellow one is made out of Potentilla petal sections.

Both species of leaf-cutters are nesting in the bee hotel, the smaller I believe is M. centuncularis and the large, M. willughbiella.

Here a female M. centuncularis, recognisable by her all orange pollen brush and marked white striped abdomen, works on the yellow nest.

Reference

John L. Neff and Beryl B. Simpson. 1991. Nest Biology and Mating Behavior of Megachile fortis in Central Texas (Hymenoptera:Megachilidae) Journal of the Kansas Entomological Society, 64: 324-336.

The Golden beetle

2011-06-29T22:48:00.002+01:00

This shy beetle is a darkling beetle, Lagria hirta. It is found on foliage or on flowers, and appears to be attracted to light so if often comes inside buildings during its short adult life. It flies around July. The larvae, in contrast, is long lived and feeds on decaying vegetable matter from the autumn to the next summer. The adult plays dead when disturbed an is quite sluggish. Males have much larger eyes (below) than females, and both are covered on a shiny golden hairy coat.

Female.

Male.

Wasp and teasel water cup

2011-06-27T21:57:00.001+01:00

Wasps make their nests of paper which requires mixing chewed wood with saliva, so they need to drink a lot. These wasps, however, were drinking from a risky source of water. The water-filled cups of teasels, where many insects and other bugs drown, and whose juices increase the teasel seed set. Although the unfortunate prey of the teasel might have just happen to fall in the cups, the lure of available water on a sunny day could also be a reason insects are lured to the cups, and many bees and wasps must fall prey to this carnivorous plant (check the wonderful blog Cabinet of Curiosities for an example). These wasps were lucky, they held on, quenched their thirst and flew away.

Hey, baby!

2011-06-25T21:12:00.002+01:00

Under the holly, on the leaf litter, wolf spiders (possibly Pardosa amentata) bask in the sun. Most females carry bulging egg sacs under their abdomens, while trying to find the best position to get warm. Several males move about, approaching a female with tentative steps, then tiptoeing, vibrating their front legs and black palps, and moving his palps alternating one up, the other down, as soon as he is very close (photo above).

The male from the top photo, gets a bit closer. This female is carrying an egg sac and snaps at him.

He quickly retreats and starts stalking the next female...

This one does not have an egg sac. Will he be lucky this time?

No, rejected again. A short moment of rest with the male and two females basking nearby

A female with a very large egg sac. The spiderlings must be close to emerge.

UPDATE 6/12/11: a little video taken on the day of one of the courting males:

Multiple mating Narcissus flies?

2011-06-24T22:39:00.001+01:00

I took some shots of Narcissus flies, Merodon equestris, mating this sunny morning on a dandelion flower. Initially there seemed to be two males, but one of them left. Editing them tonight I realised that the male that left had been mating to start with, and then the other male had mated with the female as well. The male mounting the female beated his wings continuously as if in flight, and the female used her long rear legs to half-heartedly swat at the male.
This is the sequence of shots showing both males mating in succession with the female.

The male behind the female is mating, the one on top beats its wings

The first male is dislodged

The second male mating (also in the top shot)

I have been unable to find - or access - published research about Merodon mating behaviour or how frequent this multiple mating is. It is also possible that I missed a struggle between the males and the second managed to dislodge the first one. After mating, the female will look for daffodil or bluebell bulbs to oviposit. The larvae will feed on the bulbs and these will die or bear no flowers next spring.

Buzzing bees in poppies

2011-06-24T21:44:00.001+01:00

There were lots of poppies around today, and they buzzed with a high pitch produced by the bees and bumblebees inside, often more than one, gathering their almost black pollen. Poppies are unusual flowers, bright red, bowl shaped, with black centers and radial symmetry, and they do not produce nectar, just lots and lots of edible, protein-rich pollen. Poppies open at dawn, and before they do, their anthers start to release pollen. By the following day, fully fertilised and depleted of pollen, the flower loses its petals. Although the red and black colour combination of poppies - like some tulips and other Mediterranean flowers - is through to have evolved to be fertilised by beetles, bees and bumblebees take advantage of the pollen bonanza offered by these short-lived flowers. Bumblebees do not need much time to learn how to collect nectar, even from complex flowers, but pollen collecting is much trickier. The powdery pollen needs to be released from the anthers, brushed from the bees hairy body, mixed with nectar to make it sticky, packed into pellets and fixed to their corbicula, the specialized area on their legs adapted to carry the pollen. Nigel Raine and Lars Chittka, from Queen Mary University of London, carried out some experiments in a greenhouse to investigate how bumblebees learn to collect pollen. They used freshly collected poppy flowers from a field nearby before each bumblebee foraging trip, and tested six Bombus terrestris bumblebees that had never collected pollen before.

The figure above shows how pollen from the wild collected poppies drastically decreased along the morning - as the wild bees outside collected it - by 9:00 am there wasn't much left. The researchers then computed the rate at which their bumblebees collected pollen from the poppies, related to the available pollen at each foraging bout, by removing and counting one of the pollen pellets brough to the colony after each foraging trip by each bee.
Bumblebee pollen collection behaviour markedly changed with experience:

During their first few visits, all bees were surprisingly clumsy, one bee even failed to collect any pollen during its first foraging bout despite making 56 flower visits. In the early stages of their foraging career, bees were observed to collect pollen loads that fell apart, or were so large that they fell from the bee’s corbiculae (pollen baskets) before reaching the nest. As each bee gained foraging experience, the frequency of such events rapidly declined. Bees also changed how they used ‘buzzing’, a technique of holding the anthers in their mandibles while vibrating their flight muscles, to facilitate pollen collection. While naïve bees typically buzzed either all or no flowers, skilled foragers would selectively ‘buzz’ flowers containing less pollen.

The following graph shows how foraging efficiency increases with foraging trip, indicating that bees learn to be more adept at collecting pollen. Despite this, the bees seemed to forget most of what they had learn overnight, as efficiency was much lower in the first trip of the second day than in the last trip of the previous day. :

A honeybee and a bumblebee share an Opium poppy

References
Raine, N., & Chittka, L. (2006). Pollen foraging: learning a complex motor skill by bumblebees (Bombus terrestris) Naturwissenschaften, 94 (6), 459-464. DOI: 10.1007/s00114-006-0184-0
Dafni, A.; Bernhardt, P., Shmida, A., Ivri, Y. and Greenbaum, S. (1990). Red bowl-shaped flowers: convergence for beetle pollination in the Mediterranean region. Israel Journal of Botany, 39, no1-2, pp. 81-92, 81-92 Other: 0021-213X

A Hawthorn Shieldbug

2011-06-23T21:21:00.000+01:00

We came across a couple of Hawthorn Shieldbugs, Acanthosoma haemorrhoidale, on a large hawthorn hedge at the edge of our local park yesterday. This is a strong contender for the most beautiful British shieldbug, large and shiny, with bright green and red markings, finely punctured and with broad, pointy "shoulders". They are found in a range of trees and shrubs, but their favourite food is haws, the berry produced by the Hawthorn, although they also feed on leaves or other fruit such as apples, piercing them with their rostrum, their sucking, needle-like mouthpart. As other shieldbugs, they overwinter as adults, often darkening their colours at the end of autumn, and emerge in the spring to feed and mate. Eggs are laid around May and the nymphs develop during the summer into increasingly larger stages quite different in colour to the adults. The new adult generation would emerge in August.
Until recently, the Hawhorn shieldbug was common only in southern england, but his distribution has expanded north recently and now can be found in Scotland too.

A Hawthorn Shieldbug on Hawthorn

Final stage Nymph (2nd August 2008)

Nursery web spiders

2011-06-22T22:24:00.002+01:00

The nursery web spider, Pisaura mirabilis, is a striking, handsome spider with a surprising range of behaviours. A large spider, with long, but solid, legs and a long, tapering abdomen, it is quite variable in colour, but it always has a pale band in the middle of the carapace, flanked by darker bands. It is found in a range of habitats including grassland, meadows, woodland rides and gardens. Pisaura does not build a web, rather it is an active, highly visual hunter on low vegetation or the ground.

In the words of Michael Roberts:

When at rest or sensing prey, they often extend the first and second legs and hold them together, straight out at an angle. Pisaura does this on vegetation, sitting quite still with the first pairs of legs held up, and seems almost like a dog sniffing the air.

In the summer, the young spiders mature and males wrap a captured prey into a silk parcel as a nuptial gift for the female, a unique behaviour amongst spiders. Although this might represent some form of paternal care, it is likely that it originated as a way for the male to protect himself from sexual cannibalism, which is very common in spiders, and also occurs in Pisaura, often before mating takes place. The male will carry the gift around until he finds a mature female. He will offer her the gift in a ritualised way and if she accepts it and starts feeding on it, copulation will ensue. Females not being offered a gift will not mate. Occasionally the female will interrupt mating and the males display another unusual reproductive behaviour: if the female behaves aggressively or tries to snatch the gift, the male will feign death, a common antipredator behaviour in spiders called thanatosis. He will remain motionless, with legs stretched while being dragged by the female, but still hanging onto his nuptial gift with his jaws. If the female starts opening the present and feeds, the male "comes alive" again and mates. Feigning death is a behaviour that increases male reproductive success, as was shown in experiments by Line Spinner Hansen and coworkers. They found that males feigning death have more copulatory success than males who don't. They explain these results by the fact that males feigning death achieve longer copulations, and are able to continue in contact with the female and resume mating later, for example when females try and run away with the gift.

(from Spinner Hansen et al 2008)

Females make quite large, pale egg sacs which they hold under their bodies with their jaws and palps (top and above), and walk awkwardly on tiptoes white they do this. When the female senses that eggs are about to hatch she constructs a nursery.

She opens the egg sac and folds some blades of grass and builds a loose tent of silk strands around them. The she mounts guard just underneath her nursery. When the spiderlings hatch around midsummer, they form a cluster in a similar way to the Garden Spider, in the safety of their tent, where remain until after their second moult they disperse. I found the one above this afternoon in my local wildlife garden. The spiderlings are visible at the edge of the tent. I am so pleased to have a thriving population of this amazing spider living at my doorstep.

References
Roberts, M.J. (1995) Spiders of Britain and Northern Europe. Harper Collins, London.
Spinner Hansen, L., Gonzales, S., Toft, S., & Bilde, T. (2008). Thanatosis as an adaptive male mating strategy in the nuptial gift-giving spider Pisaura mirabilis Behavioral Ecology, 19 (3), 546-551 DOI: 10.1093/beheco/arm165
Bilde T, Tuni C, Elsayed R, Pekár S, & Toft S (2006). Death feigning in the face of sexual cannibalism. Biology letters, 2 (1), 23-5 PMID: 17148316

...and dying

2011-06-21T20:56:00.000+01:00

The above shot completes my Philadelphus series. This crab spider, the same individual featured on the previous post, trapped a fly that had come to feed on the flowers.

Feeding, hunting, resting, mating...

2011-06-18T23:40:00.002+01:00

Around the summer solstice, the Philadelphus or mock orange blossoms. In addition to its lovely scent, its broad, cup-like white flowers make a beautiful background for insect photography. It is just fitting that insects love these flowers too. The following photos were taken yesterday and today.
Small spiders such as this crab spider (above) sit on the flowers to ambush flying insects attracted to them. Small garden spiders build their webs also amongst the blossom.

A fly resting

Carpet beetle (Anthrenus sp.) feeding on pollen

Greenbottle (Lucilia sp)

Bumblebees often feed on the blossom. Here, Bombus terrestris.

A mating pair of ichneumon wasps

A small bee (Hylaeus?) enjoying the pollen

Invasive Harlequin parasites

2011-06-16T23:19:00.025+01:00

Every day on the way back from work I walk next to this wall. The other day there were plenty of cannibal Harlequin ladybird larvae eating prepupae. Today there were many more pupae and a few prepupae. I have no idea how I noticed this tiny fly on the head of a prepupa. The ladybird pupa shook its body back and forth to no avail. Later I identified the fly as a scuttle fly, genus Phalacrotophora. Some species of this genus are endoparasites of ladybird pupae. The fly mounts guard on a prepupa and when it pupates it lays some eggs underneath. The fly larvae on hatching parasitise the ladybird and when fully developed they emerge and pupate on the ground. A common hypothesis on the rapid spread of invasive species is the "enemy release" hypothesis. This states that the invaders in the new range lack specific enemies - pathogens, parasites or predators and that this allowes uncheckered population growth. The success of the harlequin ladybird has been hypothesized to depend at least in part on escape from natural enemies. Recent studies indicate that generalist ladybird parasites might be starting to attack this ladybird in the invaded range and this includes pathogenic fungi, and endoparasitic nematode worms, wasps (Dinocampus coccinellae and Oomyzus scaposus) and flies. Prevalence can be quite high, with up to 33% of specimens in Danish samples infected with nematodes, but, on the other hand, lower fitness from the parasitoid Dinocampus reared from Harlequins, suggest than some of these enemies have yet to adapt to this invasive ladybird. If you live in the U.K. there is a survey you can take part into, by collecting ladybird pupae and rearing them, and then reporting what comes out of them (see the Ladybird Parasite Survey website).

References
Koyama, S., & Majerus, M. (2007). Interactions between the parasitoid wasp Dinocampus coccinellae and two species of coccinellid from Japan and Britain BioControl, 53 (1), 253-264 DOI: 10.1007/s10526-007-9138-5
Kenis, M., Roy, H., Zindel, R., & Majerus, M. (2007). Current and potential management strategies against Harmonia axyridis BioControl, 53 (1), 235-252 DOI: 10.1007/s10526-007-9136-7
Durska, E., Ceryngier, P., & Disney, H.L. (2003). Phalacrotophora beuki (Diptera: Phoridae), a parasitoid of ladybird pupae (Coleooptera: Coccinellidae) European Journal of Entomology, 100, 627-630 Other: 1210-5759