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.