Bark at the Moon - small invertebrates of timber (Part 4)

After yesterday's brief journey off-topic (sometimes it just has to be done), I'm back to the tiny invertebrates found in our firewood store. As promised, I've started looking at the sub-2mm critters I must say are proving tricky. This is not because of their small size as such - after all, I have microscopes - but because they include taxa which are relatively unfamiliar, not only to me, but given the lack of literature covering some of them, to entomologists more broadly. There are also difficulties associated with handling them without damage (tiiiiny tweezers, small brushes) and storing them without some of the soft-bodied organisms shrivelling to almost nothing. This has as much to do with my lack of curatorial expertise with such species as anything else. However, there is an up-side; these issues probably mean there are some under-recorded species among the bark and dead-wood (saproxylic) invertebrate community and hence some interesting records if I can make species-level determinations. First up, another barklouse or 'psocid'.

A head-on view of a barklouse. The tiny size is highlighted by using the individual lenses (ommatidia) of the eyes as a rough idea of scale.

Although it can't be seen in the photo above (due to the specimen having shrivelled I think - it's still there but very faint), there is a diagnostic anchor-shaped mark on the 'face'. The wings are reduced to tiny buds and the abdomen has several rows of dots, still visible and appearing as round 'bumps' here, though their bumpiness is a bit of an optical illusion. This is the widespread Cerobasis guestfalica which has been spread internationally through commerce such as the timber trade. Almost all specimens found are females (males occur very very rarely) which means most poulations are entirely parthenogenetic i.e. they reproduce without fertilisation by a male (New, 2005). Moving back into my comfort zone - beetles - I managed to find a single specimen of a 1.6mm bark beetle.

Note the elongate shape, rounded antennal segments and longitudinal lines on the elytra and pronotum.

A close-up of the pronotum. The hind (left) angles have a tiny tooth and there are two slightly raised lines on each side of the pronotum - the inner one is quite clear, the outer one less so, though it can be seen as a broken bright line.

This beetle is in the family Laemophloeidae - not a group I am very familiar with - and to identify it, I needed to go back to Joy (1976). The features above did however allow identification as Cryptolestes duplicatus, a species which is probably predatory and/or parasitic on the larvae of other beetles. This species has a scattered, localised distribution in south and south-east England; not rare as such but not common either, and I suspect under-recorded (as well as having seen some significant taxonomic changes which have moved it from the genus Laemophloeus within the family Cucujidae), so quite a good find. Feeling bold, I thought I'd move onto something really small - a mite (so, an arachnid rather than an insect).

A mite showing the hard surface with a few long hairs (and some bits of plant material stuck to it!), but no velvety covering as seen in the more familiar 'spider mites'.

For now, I'm not going to try to identify this - I don't have much literature covering the mites, though I do think it is in the family Acaridae, based on its overall form. However, if I feel keen I might try later, in which case an update will appear here.

So, what next for the 'Bark at the Moon' series? Well, I still have some specimens to identify and I intend to continue collecting, so although posts in this series may slow down a bit, I strongly suspect there are more to come. After all, how else to investigate these under-recorded groups..?

References

Joy, N.H. (1976). A Practical Handbook of British Beetles (2 vols.). Classey, Faringdon. (This is the resized reprint of the original 1932 classic work). A CD-ROM is also available.
New, T.R. (2005). Psocids. Psocoptera (Booklice and Barklice). RES Handbooks for the Identification of British Insects 1(7): 1-146.