November bug magnets

I went for a walk this afternoon to re-acquaint myself with my clean and repaired camera. After spending almost three weeks camera-less, it was great to have it back. I just walked back to the spot where a few days ago I spotted the B. hypnorum and waited around the sweet smelling Mahonia bushes trying to spot more bumblebees. There were flies (Bluebottles and a smaller species) and wasps around, but my patience finally paid when I saw the distinctive large and dark shaped of a bumblebee amongst the flowers. Not a B. hypnorum, but a worker B. terrestris, stayed just for a few shots (top).

 The second bug magnet today was Ivy. There were dozens of male wasps feeding on Ivy flowers on the wildlife garden. Their large antenna reminded me of mountain Ibex males. I am not very good identifying wasps, although in a post in WAB today somebody pointed at a very informative webpage to identify them. I will update the post if I manage to get an ID. Around the ivy there were also feeding Bluebottles and a parasitoid wasp.
 The third bug magnet was a non-native bush related to the Ivy, the Fatsia japonica. Here the ubiquitous bluebottles were the only insects around.

Winter active bumblebees

We had our first frost yesterday, and it was also a frosty morning today. But coming back home this afternoon, with the light already going weaker, I came across a Tree Bumblebee, Bombus hypnorum feeding on a large Mahonia bush. I have posted before on this bumblebee, a recent natural colonist in the U.K. In the last two decades, reports of winter active bumblebees - mostly Bombus terrestris - have steadily been accumulating, especially in the south of Britain. Queen bumblebees are occasionally active in warm winter days, but the reports referred to queens collecting pollen - a sign they are actually nesting, not hibernating - or workers - indicative of active nests. These observations depart of the usual bumblebee life cycle in northern Europe, where winter hibernation of queens is the usual case. Whereas there are many native flowers in bloom during the winter to support a second generation in the Mediterranean, this is not the case in northern Europe. What resources are active winter bumblebees using? Stelzer and coleagues tested the hypothesis that winter bumblebees are making use of non-native flowers in parks and gardens. To do this, they set up B. terrestris colonies and followed them during two winters. In the second winter they introduced a new technique - micro-tagging - which allows automatic recording each time the tag passes nearby the tag reader set at the nest entrance. They attached the small RFID tags to the thorax of 64 individuals, and positioned a micro-balance at the entrance of the nest so that bumblebees also weighed themselves as they went in and out the nest, so that they can estimate the increase of weight of each bumblebee at the return of each foraging trip. Their results showed that bumblebees in their experimental nests were able to forage for nectar successfully during the winter, with nectar returns per hour foraging comparable or higher to yields obtained during spring and summer.

The researchers also carried out transects in the Royal Botanical Gardens in Kew to ascertain which plants were being visited by Bumblebees during the winter:
Only cultivated plants were in flower and the main plants visited by B. terrestris were Arbutus unedo and Salvia uliginosa in October (38.2% and 42.3% of the total recordings during that month, respectively), Arbutus spp. (A. unedo and A. x andrachnoides) (31.2%) and Mahonia spp. (Mahonia x media ‘Winter Sun’, Mahonia x media ‘Charity’ and Mahonia lomariifolia) (43.7%) in November, Mahonia spp. (69.0%) in December, Salix aegyptiaca in January (48.2%) and Lonicera fragrantissima (24.1%) in February.

The high yields obtained by the experimental bumblebees might be explained by the nectar sources being large bushes with large volumes of nectar per flower and the flowers being in large inflorescences, such as the ones in Mahonia (see photo above) and willows. In addition, there is no competition for nectar and pollen in the winter months by other foraging bees. Only a few honeybees were around, and these are not active below 10oC, while the bumblebees can forage at temperatures close to 0oC. Further work is necessary to assess if this generation is actually successful, that is, if males and queens are produced, but these results show how human impacts - gardening possibly coupled with climate change- have unexpected effects on the life cycles of native organisms.

Stelzer RJ, Chittka L, Carlton M, & Ings TC (2010). Winter active bumblebees (Bombus terrestris) achieve high foraging rates in urban Britain. PloS one, 5 (3) PMID: 20221445

Cameraless

I made the mistake of taking photos in a beach on a windy day (what was I thinking?!). You don't need to have much imagination to guess what happened. Some tiny grain of sand got in the camera and it stalled with the objective open, then, an ominous bleeping and a warning 'lens error! restart camera!'. After that, I did some frantic searches in Google to find a simple solution and failure to restart the camera after trying various tricks. The consequence, my Powershot G10 is being now sent to a repair centre, and while I wait, my dear old G6 was rescued from a cupboard and put to action. Now, when you get used to an upgrade you often do not notice the jump in quality, probably as you are often frustrated trying to get used to the new buttons and getting aquainted with you new toy. But going backwards, that's tough. I miss my G10 so much! I miss the image stabilization, I miss the large, bright LCD screen, the optical zoom, the top dial to adjust the aperture...

 However, I am so glad this happened at the beginning of november, when Bugblog is feeling a bit sleepy and cold, almost ready to hide under a curly leaf and go into hibernation. I would have been straight to the shops to get myself a G12 if this had happened in the summer. And still, some bugs still refuse to believe that, yes, it is cold and time to hide! While gardening this weekend, I was accompanied by the surprising buzzing of honeybees foraging on the fuschia, I disturbed a healthy female Tegenaria when moving a compost bag. I also came across this tiny snail, probably born only this summer, having a walkabout. Despite all of the above, when I saw the photo above I realised I can survive without my G10...at least for a few days.

Scary spider story

For a belated Halloween celebration how about some cannibalism on spiders? I have posted before on maternal behaviour in spiders, but, after coming across this species a few times in the last few days (a male above) I had to write on its bizarre, and utterly horrifying behaviour. Amaurobius are common spiders, with three British species which often live on holes in house and garden walls, fence posts or tree trunks. Their holes' entrance is surrounded by a characteristic radial and random web of white silk, with adheres to prey like velcro. These spiders are mainly nocturnal and can trap relatively large prey such as bees and droneflies, presumably as the sit nearby the entrance hole.

Amaurobius hole in a wall...

...and its owner with a trapped a dronefly

The unusual behaviour relates to reproduction. Females lay their egg clutch during June and July inside their holes and sit over it for three weeks, when she opens the egg sac and the spiderlings hatch. The interaction between the spiderlings and their mother stimulates her and inhibits the maturation of the eggs of a second clutch. The female is not agressive and instead solicits the young to migrate to her ventral side and lays immature eggs, the so called trophic eggs, for the spiderlings to eat. 

(from Kim and Roland 2000)

Spiderlings deprived of this extra food do not survive as well, and gain weight much more slowly. A few days later, the female dies and the spiderlings promptly cannibalize her, gaining further weight and increasing their chances of survival when they disperse. The trophic eggs are fertilized and apparently viable, so the female is actually increasing the survival of her first clutch by sacrificing a possible second. Does she produce more or less offspring overall as a result? Kim and Roland, in experiments in which they compared spiderlings with access to trophic eggs with deprived spiderlings, estimated that the mother produced an average of 104 viable spiderlings of the first clutch at day 6 when fed with trophic eggs, compared with a total number of 102 when they removed females from the first clutch and allowed to lay again. This similar number of total spiderlings is, however, misleading as six out of the 10 females removed from their offspring either had abortive clutches or ate them themselves, suggesting that the viability of the second clutch as a replacement clutch is decreasing and the eggs of the second clutch could be specialising in their function as trophic eggs. Trophic egg feeding might have evolved as a way of reducing intra-clutch cannibalism at a time in the spiderling's life when they cannot produce the sticky silk required to catch their own prey. Next time you see Amaurobius holes in your wall, spare a thought for these hair-raising behaviours happening so near you at night.

More information

Kim KW, & Roland C (2000). Trophic egg laying in the spider, Amaurobius ferox: mother-offspring interactions and functional value. Behavioural processes, 50 (1), 31-42 PMID: 10925034

Ten bluebottles sitting on the wall

Posts in BugBlog are necessarily becoming spaced out now. Although we have not had a frost yet, days are colder and darker heralding the arrival of winter, and insects are becoming scarcer by the day. Sunny today, there were still some bugs around. There were several active spider species: Garden spiders, Mouse spider, Linyphia triangularis, Amaurobius and Zygiella. The garden spider female above hangs her web every day just outside the kitchen window. I liked the effect of the ripe cotoneaster berries in the background.

We came across this colourful Birch Bug, Elasmostethus intersinctus, while gardening. I identified it using the site British Bugs A great resource on hemipterans.
Greeting me early in the morning this bunch of bluebottles sunbathing on a fence. There were more than ten, but they reminded me of the song...

A harvestman, Opilio canestrini with legs outstretched on the wall.

Honeybees were the first active bees of the year and by the look of it, they are going to be the last ones too. A few are feeding on the Fuschia in the last few days. 

The positive aspect of the relative scarcity of bug activity in the garden is that I can actually do some gardening without having to rush every two minutes to the house to fetch the camera!

The fast woodlouse

I have featured two common woodlice species before. There is a third common garden species, the fast woodlouse, Philoscia muscorum. As it name implies, it is quite fast, with long legs that keep its body well above the ground. Its dark, rounded head, and a longitudinal dark stripe along its shiny, marbled body, make it easy to identify (for a simple key to ID British woodlice click here). The fast woodlouse is a native European species which is also found in the U.S. It is of medium size (around 1 cm.) and inhabits a range of habitats from sand dunes to woodland. A P. muscorum population living in the dunes of Spurn Head investigated by Grundy and Sutton showed the phenomenon of year-class splitting. This means that there are two reproductive strategies amongst individuals born each particular season. The 'fast growers' reproduce when they are one year old and die, the 'slow growers' breed for the first and only time when they are in their second year.

Figure from Grundy and Sutton 1989. Note that the dark (slow) growers are joined in their second year by a new cohort (in grey).

Grundy and Sutton's experiments showed that females only reproduced with they reach large size and they have one or two broods (rarely three) with an interbrood period of 5.4 weeks. This and the positive relationship between temperature and growth rate means that most individuals born in the first brood are able to reach a large size before winter sets in and start growing faster when the breeding season arrives. Most individuals born in the second brood (a bit more than a month later) miss out on the benign growing conditions and are too small after the winter and when the next breeding season arrives they are still too small and waiting until the following breeding period makes sense to maximize their chances of reproducing successfully.
More information
Grundy, A. & Sutton, S. (1989). Year class splitting in the woodlouse Philoscia muscorum explained through studies of growth and survivorship Ecography, 12 (2), 112-119 DOI: 10.1111/j.1600-0587.1989.tb00829.x

A dipluran

Lifting a stone sometimes feels like opening a door and peeking into an alien world. A world inhabited by shy, unobtrusive creatures, going about their business. Our lives might never cross even though we live so close to each other. One such creatures are the diplurans. You might have never heard of them - they were actually only discovered at the beginning of the 20th century - despite being cosmopolitan, most likely due to their soil-living habits. Diplurans are hexapods, the six-legged group of bugs to which the insects also belong. They are, in contrast to them primarily flightless, blind - they have no eyes or ocelli - and whitish in colour. They are often tiny (less than 5 mm), the one in the photo closer to 2 mm and have long, beaded antenna. Their most distinctive feature is the presence of two cerci at the end of their abdomen. Today, under the same stone where rove beetles were hiding some days ago, I found a pair of diplurans. They run frantically looking for a new hiding place, checking each piece of soil attached to the stone and keeping their large cerci lifted from the surface. I find it relatively easy to take photos of them as their colour contrasts sharply with the dark soil. Just 12 species have been described in the UK. The one above probably belongs to the genus Campodea. They are mainly detritus feeders - although some species are predators, feeding on mites and other small organisms - and lay their eggs in clusters. They moult many times throughout their lives and have some capacity for regeneration.

A fragment of an early note on British Campodeidae (from the Biodiversity Heritage Library; Bagnall (1915) Preliminary notes on British Campodeidae (Thisanura).The Entomologist Monthly Magazine, 51:262.

Peeking under stones

Every now and then I lift some stones in the garden and check what's living under them. It is not a great strategy to observe bug behaviour, as the stone-lovers tend to be light-haters and rush frantically trying to hide again. However, this month it has turned out to be a good strategy to spot species I haven't blogged about yet. A large male earwig, Forficula auricularia, with its formidable pincers. Then, I disturbed the underground nest of some garden ants, Lasius niger. Although eggs and larvae couldn't be seen - probably too superficial for that - a tiny inhabitant of ant nests could be seen, some albino springtails, Cyphoderus albinus. If you click on the photo you will probably be able to make it out towards the left of the centre of the photo, next to an ant's head. Although easy to spot due to their white colour and highly mobility, their small size - probably no more than a mm in length -  made them quite tricky to photograph.

Finally, a couple of rove beetles (or Devil's Coach Man) Ocypus nero, one of them pictured below.

In addition, I found stones literally carpeted on rough woodlice, some earthworms and plenty of slugs.

Communal daddy long legs

These three daddy long legs (Opiliones), Paroligolophus agrestis, had found a cosy spot at the top of this apple. I am not aware that this species is particularly gregarious, although many daddy long legs do not dislike each others company and some actually form dense aggregations. The function of the social behaviour of daddy long legs is poorly understood and the explanations range from thermoregulation to defence. Although most individuals aggregating are adults, mating does not seem to explain this behaviour. The following video shows an instance of mass aggregation in Daddy long legs:

Tegenaria male

I have posted before on male Tegenaria spiders starting searching for females at this time of the year. I came across one this afternoon under the cat's bed. It has taken me a while but I am forcing myself more and more to use the flash, especially now that the days are shorter and strong natural light is a commodity we don't came across that often. With a built-in flash a straight macro shot gives a large shadow where the objective blocks the flash light, but I avoid this shadow falling on the target by first focusing on the target and tilting the camera to one side to shoot, and alternatively, by using the zoom. A bit of cropping and voila! shadow gone.

The late bumblebee

A sign that the bee season is coming to an end when the only bumblebees visiting the lavender are carder bees Bombus pascuorum. There might be still a few queens of the other species around, but this handsome ginger carder bee is still in peak season, making use of the late summer flowers around. This bumblebee has a relatively large tongue (average of 8.5 mm) which allows it to use deep flowers, even foxgloves (above, a worker in mid June leaving a foxgloves against the dark background of my rubbish bin) and Iris, as food sources.
Other than in Lavender, at this time of year, they can be seen foraging on Verbena bonairensis, Sedum spectabile, Agapanthus, Sunflowers, Caryopteris, Cytisus, Buddleia, Nasturtium, hardy Geranium, Salvia, Honeysuckle and Purple toadflax.

Males (above) and queens appear at the end of the summer and the species can be seen actively flying until the first frosts. They nest on the ground and actively comb moss to insulate their nests. For a little video of a B. pascuorum nest click here.

Celebrity flies

Continuing with the topical apple subject, I have been leaving damaged and rotten apples on the soil of a large pot. The place now is heaving with tiny fruit flies of the genus Drosophila - possibly the most famous and best known fly in biology, D. melanogaster. It is difficult to give an idea of how much research has been carried out using this fly but a quick search on the Google Scholar academic search engine yielded today under 3,000 hits on the common earwig, while D. melanogaster had 324,000 entries. Since the beginning of last century, experiments on fruit flies have generated much of the basic knowledge of genetics and evolution, and their genome sequence was published in 2000, before the human genome. Among the many reasons they have become such a popular model organism is that they are ubiquitous, easy to keep (who doesn't have fruit flies around the compost heap or fruit bowl?) and reproduce rapidly producing many eggs.
Much research has been carried out on fruit flies mating behaviour and the influence of genes on it. Despite their tiny size fruit flies can be easily watched performing their mating rituals on top of the rotting apples. Males are smaller and with a larger dark patch at the end of their abdomen. Females have a more stripy, and often distended abdomen.
According to Marla Sokolowski:

It might come as a surprise to some that D. melanogaster shows many exquisitely performed and complex patterns of behaviour. For example, the male fly shows courtship behaviour that is full of sensory stimuli and that requires the female to hear his song, feel his taps and licks, smell his odours and visually evaluate his stature...

As a primer, this figure (also from Sokolowski, 2001) illustrates the main steps of the fruit fly mating behaviour. Male 'song' is produced by wing vibration while keeping the wing tipped forward.

Check out the Drosophila melanogaster Wikipedia page for more info.

The lion springtail

Every day I go out in the garden and fetch the few apples that have fallen overnight. This springtail, Orchesella villosa, was resting on top of one today. It sat nicely for me and then jumped to pastures new.

Shiny red ladybirds and apples

We have been picking some apples today. Our tree is of the variety Red Devil and crops beautifully large sharp, tangy and red-fleshed apples. After picking one of them, we uncovered four 7-spot ladybirds nestled together, thinking themselves all ready for winter. They will have to look for a better spot as the apples won't be in the tree much longer. Ladybirds often overwinter in groups, but this is the largest group of 7 spots I've seen.

September bugs

There is a definite autumnal feel these days. Shorter days, ripening berries and leaves already changing colour. September, however, is a month plentiful on all sorts of bugs. During a walk in our local Millennium Wood, Oppy Wood today, we spotted five butterfly species, Comma, Speckled Wood, Small Tortoiseshell, Red Admiral and Large White. We watched Commas and Speckled Woods sucking the sweet juice of ripe Blackberries.

There were plenty of Daddy Long Legs (tipulidae). Some of them mating.

A couple of Migrant Hawkers patrolled above our heads. A male (top) eventually stopped to rest, hanging from some low branches. He let me get really close to him for some shots.

There also were grasshoppers about - possibly Lesser Marsh Grasshopper, Chorthipphus albomarginatus - 7 spot ladybirds, froghoppers and wolf spiders.

A male Lesser Marsh Grasshopper

A forest bug

I realised a few days ago that I have not posted much about bugs (Hemiptera) in BugBlog. To start making amends, here comes a short one on a common bug these days, the forest bug Pentatoma rufipes, a quite large, showy shield bug easily to recognise for its spiky lateral thorax projections and orange legs. There are quite a few bug species about, many still nymphs, but an adult forest bug landed on my shoulder yesterday. Forest bugs lay their eggs on bark of oaks and other trees around this time of year and the nymphs hibernate on the trees. The adults are partly predatory. For lots of information and beautiful photos of British bugs here.

Hunter hunted

I feel like apologising for posting on Pholcus spiders again, but the reason is they are everywhere in my house. I read somewhere that hoovers are their most feared predators, but today I came across a chunky-looking spider, a mouse spider, Scotophaeus blackwalli (than you to No. 9 Spider from Wild About Britain for identifying it for me) holding a Pholcus on her fangs on the kitchen ceiling. I climbed on a stepladder to get some close shots, although I couldn't get as close as I wanted. The Pholcus' spindly legs stood aside while the mouse spider finished its meal. After a few minutes, the mouse spider left the Pholcus empty carcass behind. It made a change from the Pholcus being the usual spider predator in the house.

A side view from the mouse spider

UPDATE

For a beautifully filmed video of a house spider vs a Pholcus spider see

Mummy long legs

My outside toilet is a Pholcus phalangioides haven. These long legged spiders hang upside down from every existing corner of it. One of them yesterday sat proudly over her 30 or so offspring. I had seen her in the same spot on previous days with her egg sac in her mouth, but this is the first time I see this spider's newborns. They are quite ghostly looking, with transparent legs and thorax, their dark eyes and brownish abdomens the only colour in them. This is a cropped image with a close up of some of the baby spiders.

Spider chat up lines

In summer and autumn, spiders become more noticeable. The tiny spiderlings born in the spring have now become adults and males are wandering in search of females. One of the most common spider species in the UK is the elegantly marked Linyphia triangularis (female above). This spider makes a sheet web with criss-crossing silk lines over it in low bushes and trees. The spider hangs belly up from the underneath the sheet. Flying insects colliding with the transversal lines  fall onto the sheet, where the spider traps them. Yesterday, while photographing 7-spot ladybirds I came across a pair of L. triangularis. The male made jerky movements with its chelicerae and palps and the female replied.

Male (on the left) and female Linyphia triangularis. Note the male's large fangs on the bottom photo.

Unfortunately, I seemed to have disturbed them and the male retreated, so I didn't see the end of the interaction. Field experiments carried out by Nielsen and Toft showed that male L. triangularis use what are known as 'alternative mating tactics'. Males guard subadult females just prior to their final molt in order to access them while they are still virgin, possibly due to a strong sperm preference which results in males mating with a virgin female fathering most of the female's subsequent offspring. These researchers took advantage of this behaviour and took 56 males and paired them with females in the field. Once this relationship was established they introduced an 'intruder' and recorded what happened up to the point when the female was mated. In 64% of the cases, the males resolved the dispute about the female by fighting using their large chelicerae. Larger males are better at winning these direct conflicts. But in 36% of cases, males used a different strategy called 'interference'. After losing a fight, they hang around and 'distract' the courting pair trying to chase the winning male away from the web. They actually succeeded and mated the female first in 7 occasions (12% of all conflicts) showing that this strategy - which is adopted by small males - can pay off. Additional observations suggest that smaller males hang around and try and mate with the female (not virgin at this stage) probably winning some residual paternity in the process.

 In a different study, Funke and Huber carried out detailed measurements of males and females genitalia and cheliceae (see figure above) and found out that male chelicerae (including the oversized fangs) grow faster with body size than genitalia, indicating strong directional natural selection on this trait due to the large effect on male-male conflict in their fights for females.

More information
S. Funke and B. A. Huber (2005). Allometry of Genitalia and Fighting Structures in Linyphia triangularis (Araneae, Linyphiidae) Journal of Arachnology, 870-872 DOI: 10.1636/S04-16.1

Nielsen, N and Toft, S (1990). Alternative male mating strategies in Linyphia triangularis (Araneae, Linyphiidae). Acta Zoologica Fennica