Sunday, 24 October 2010

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 triangularisAmaurobius 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!

Tuesday, 5 October 2010

The fast woodlouse

ResearchBlogging.orgI 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

Monday, 4 October 2010

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.