Bark at the Moon - small invertebrates of timber (Part 2)

After yesterday's look at a species of barklouse (Psocoptera) which hasn't been known from Britain for very long, I thought I'd move on to the invertebrate group arguably most often associated with dead wood - beetles.I have so far only worked on the 'larger' (2-3mm) specimens that I collected late last week from our firewood store; tinier species remain to be identified...So, I shall begin with a broadly familiar group, the weevils (Curculionidae).

Side view showing punctures, cylindrical shape and broad, blunt rostrum.

Head showing rostrum (without a strongly broadened end or sharp basal excision) and bluntly pointed (rather than rounded) ends to the antennae.

Rear of elytra (wing cases) showing a flange round the edge (technically, formed by  outgrowth of the 9th interstice or 'gap between rows of punctures').

Using the excellent work my Morris (2002) for this often fiddly group, these features lead to identification as Euophryum confine, a now-common species in Britain; introduced here from New Zealand in 1937, it has spread rapidly and can be a pest of timber (including buildings). I'll be checking our firewood carefully before bringing it indoors!

Next, a beetle with a broadly similar size and overall form (unsurprising for wood-borers that have to fit into tunnels and small holes) - despite only being 2-3mm long, this one was quite strikingly red in colour even to the naked eye.

Dorsal view showing reddish colour and cylindrical shape.

Ventral view of the head and thorax. The spines at the front corners of the pronotum are clearly visible, as are its smooth (rather than toothed) sides. Also, the 'temples' of the head are not sharply toothed.

Dorsal view showing that the pronotum does not have a pair of longitudinal grooves.

Again, this combination of features shows it to be a specimen of Silvanus unidentatus with Hurka (2005) proving useful for separating it from the rarer S. bidentatus. This is another cosmopolitan species which can be a timber pest. However, where there are small invertebrates, there are of course others for whom they are a food source. Some insectivores are well-known - many birds feed on small insects, and some of course break into wood to find them. However, among the small invertebrates of timber, there are similarly sized predators, in this case one of the true bugs (Hemiptera).

A bug with one of the fairly typical hemipteran body shapes, more or less droplet shaped with a pointed head widening evenly to the abdomen. This specimen is short-winged ('brachypterous') and the legs are yellowish with darkened femora.

Looking more closely, the wings are clearly brownish. Note the typical hemipteran scutellum - the triangular area between the wings and the pronotum.

This time using an older publication, Southwood & Leston (1959), it was fairly straightforward to key this specimen as Xylocoris cursitans, a bug in the family Cimicidae, the group which includes the bed-bugs (which have a similar general form to this species). A widespread species in Britain, it lives under the bark of fallen trees and is predatory on small beetles, springtails and thrips, and so may well help to control potential timber pests such as those described above. Of course, being a bug-nerd, I find the 'pest' species interesting in their own right, but I still have no intention of inviting them in to eat our tasty floorboards!

So, with the larger (relatively speaking) specimens covered, the next stage of my timber investigations will be to look at some of the tinier inhabitants to see what else lurks among the bark and wood-fibres. Part 3 hopefully on its way soon...

Part of our firewood store - it has since expanded considerably - what else will be calling it 'home'?

References

Hurka, K. (2005). Beetles of the Czech and Slovak Republics. Kabourek, Zlin. An excellent and well-illustrated overview of beetles from this part of Europe; the majority of species covered are found in Britain.
Morris, M.G. (2002). True Weevils (Part I). Coleoptera: Curculionidae (Subfamilies Raymondionyminae to Smicronychinae). Handbooks for the Identification of British Insects 5(17b): 1-149. Currently the standard work for this group in Britain.
Southwood, T.R.E. & Leston, D. (1959). Land & Water Bugs of the British Isles. Warne, London. Though old, this is still very useful and is available as a 2005 reprint (and possibly CD-ROM) from Pisces Publications, which is the version I have - the original is not cheap!