Wednesday, 29 June 2011

The Golden beetle

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.

Monday, 27 June 2011

Wasp and teasel water cup

 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.

Saturday, 25 June 2011

Hey, baby!

 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:

Friday, 24 June 2011

Multiple mating Narcissus flies?

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

ResearchBlogging.orgThere 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
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

Thursday, 23 June 2011

A Hawthorn Shieldbug

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)

Wednesday, 22 June 2011

Nursery web spiders

ResearchBlogging.orgThe 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.

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

Tuesday, 21 June 2011

...and dying

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.

Saturday, 18 June 2011

Feeding, hunting, resting, mating...

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

Thursday, 16 June 2011

Invasive Harlequin parasites

ResearchBlogging.orgEvery 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).

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

Wednesday, 15 June 2011

Fine young cannibals. The sequel

ResearchBlogging.orgI never intended to write a second part for ladybird cannibalism, but walking back from work yesterday I found a wall where many Harlequin ladybird larvae had congregated to pupate. I noticed that some of the fully developed, stage 4 larvae were eating either other larvae their size or pre-pupae, a very vulnerable stage as they are soft, and attached to the substrate in preparation for pupation. The cannibals had their entire heads inside their unfortunate victims. If some of you had read the previous post and thought that ladybirds were not really cannibals for eating trophic eggs (and their late developing siblings), then think again. Cannibalism is a common survival strategy in predatory insects, and many ladybirds are cannibalistic to some extent, with the tendency varying with species. This strategy may intensify in response to several factors, such as population density, food deprivation or poor food quality. In addition, the larger the difference in larval size, the more likely cannibalism is, that is, larger larvae will tend to eat smaller ones. Harlequin ladybirds in particular are highly cannibalistic, and cannibalism is an important source of larval mortality. Larval cannibalism is expected to be selected when the benefits of canibalism outweigh the costs. Benefits include the added survival when consuming a conspecific and lowered intraspecific competition, costs include the danger of succumbing to the potential victim, injury or acquiring parasites. In addition, indirect fitness costs can be incurred if cannibals feed on their siblings. It is expected that cannibalistic species would avoid eating their siblings, and this is what S.B. Joseph and co-workers found in Harlequins. In laboratory trials in which third instar larvae (potential cannibal) where housed with a first instar larvae, either a sibling or an unrelated individual, ladybirds were almost two times more likely to prey upon an unrelated than a sibling (almost 80 of the non-siblings were cannibalised as opposed to about 45% of siblings). Siblings that ended up being eaten had to be encountered more times. Unrelated individuals were attacked much faster than relatives. All this indicated that Harlequins have kin recognition mechanisms. In a species that can attain large population densities, and therefore, where potential prey is common, it might make sense to avoid siblings. In scarcer species, a sibling might be the only chance for survival, and that might explain why sibling recognition hasn't been found on other ladybird species.

Michaud, J. (2003). A comparative study of larval cannibalism in three species of ladybird. Ecological Entomology, 28 (1), 92-101 DOI: 10.1046/j.1365-2311.2002.00481.x

Joseph, S.B., Snyder, W.E., & Moore, A.J. (1999). Cannibalizing Harmonia axyridis (Coleoptera: Coccinellidae) larvae use endogenous cues to avoid eating relatives. Journal of Evolutionary Biology, 12 (4), 792-797 DOI: 10.1046/j.1420-9101.1999.00077.x

Ware, R., & Majerus, M. (2007). Intraguild predation of immature stages of British and Japanese coccinellids by the invasive ladybird Harmonia axyridisBioControl, 53 (1), 169-188 DOI: 10.1007/s10526-007-9135-8

Tuesday, 14 June 2011

How the ladybird got its spots

Ladybird adults emerge spotless from their pupal stage. To be precise, bright yellow and spotless. In a few hours, the black pigment forming their spots becomes more and more visible. This ladybird pupated in my conservatory over a week ago. Yesterday, I noticed it had just emerged, clinging to its pupal case. The top photo was taken at around 5:00 pm. After a day, this Harlequin ladybird has got all its spots, but still needs to blush a bit.
7:00 pm, yesterday
8:30 this morning
4:15 pm today

Sunday, 12 June 2011

Fine young cannibal

ResearchBlogging.orgHave you ever come across ladybird eggs? Before today, I hadn't. They are really tiny, and the ones I found were cryptically laid on the yellow backgroun of a rose petal. I would easily have miss them but for the young larvae next to them. Look closely, and you will notice that the young ladybird larvae is eating an egg, likely its sibling. Far from odd, this is very common in ladybirds. Why would such behaviour get selected? surely ladybirds which do not canibalised their own siblings should be more successful. The key aspect is that newborn ladybirds can face substantial starvation risks. They are very small and do not move fast. Egg canibalism ensures easy access to a nutritious first meal and is likely to increases their survival. The second aspect is that this sibling cannibalism is actually arranged by their mother: they lay trophic eggs: unfertilised eggs produced for the purpose of being consumed by hatchlings. Right after hatching, ladybird larvae are soft, but after two hours or so they have hardened, and they start feeding on unhatched eggs. These include trophic eggs, but also other eggs that for some reason did not develop, or did not hatch in time: they do not discriminate between different egg types. Normally each newborn ladybird will have just one egg to feed on: the rest of the unhatched eggs will have probably been eaten by her siblings. Jennifer Perry and Bernard Roitberg showed that trophic egg production is an evolved maternal strategy in response to food availability, to minimise starvation risk of their young offspring, a long held hypothesis. In laboratory experiments, they showed that ladybird females adjust the proportion of trophic eggs they lay depending on the food conditions they have experienced. Ladybird females fed few aphids (low food conditions) produced 56% more trophic eggs than ladybirds fed on a plentiful supply of aphids. This way, ladybird mothers, despite abandoning their egg clutch are able to increase their offspring survival using information on the environment they themselves grew on.

Perry, J. & Roitberg, B. (2005). Ladybird mothers mitigate offspring starvation risk by laying trophic eggs. Behavioral Ecology and Sociobiology, 58 (6), 578-586 DOI: 10.1007/s00265-005-0947-1

Wednesday, 8 June 2011

Green Shieldbugs

This Green Shieldbug, Palomena prasina, got into our conservatory a few days ago. There are two common green shieldbug species. This one is easy to identify as its wing membranes are dark. The other one, Nezara viridula, a recent invader of the U.K., has transparent wing membranes. The Green Shieldbug is a large species, bright green, with yellowish-red legs and antennae. It flies readily and this specimen flew away from the breakfast bowl after I took its photo. Shield bugs develop from nymphs in several stages that lack wings and might resemble little to the adult. The Green Shield bug has five such instars. The adult overwinters, and before doing so, it acquires a darker, purplish colour. After overwintering, they turn bright green again. Egg laying proceeds at around June and the successive instars develop during the summer, before the new generation of adults emerges in September.
An early instar of Green Shieldbug (30 July 2010)
A fifth instar (4 Oct 2010) Wing buds are visible.

For a great website to identify British bugs, including instars, see British Bugs.