Beating the bounds at Torbreck: barkflies and beetles
Stephen Moran, our Highland insect guru, has recently developed an interest in barkflies, otherwise known as barklice or psocids. They are a group of tiny insects, some winged, which graze algae, lichens and fungi on the bark of trees and can, apparently, be readily beaten from bushes and trees. He has asked us to investigate the Assynt barkfly fauna.
Accordingly, on 28th April 2020, Gwen Richards and I set about beating the gorse bushes and Norway spruces at the edge of her garden ground at Torbreck (NC0824), having first re-assembled the portable beating tray, which was not straightforward (photo 1).
The results were sufficient to keep me busy for several days. There were indeed barkflies and beetles on the gorse, an example of which was preserved in 70% alcohol, for later examination by Stephen. He has now named it as a short-winged female of Ectopsocus petersi, a widespread species, but ‘new’ to Assynt (although seven other species were recorded in the Malaise Trap on Little Assynt in 2010).
However, the most obvious products of the exercise were small to medium-sized beetles, and this is where I may get into trouble with some folk. Such tiny beasties cannot generally be identified from photographs, even if you had the specialist gear and could keep them still long enough to count, for example, the segments of their feet and antennae, and measure their dimensions. They must therefore be collected, killed (by freezing), relaxed with vinegar vapour, carefully mounted on card with antennae and legs out-stretched, labelled with a special pen (photo 2) and examined under a stereomicroscope. An unfashionable approach to wildlife, but necessary if you want to name them.
The gorse Ulex europaeus yielded the afore-mentioned barkflies and, to my surprise, several small snails, with sinistral shells (spiralling to the left; most snails are dextral). These were tree snails Balea perversa, which I was able to identify and set free; not creatures I would previously have associated with gorse bushes.
There were two species of tiny beetles (2mm long). One keyed out readily to Micrambe ulicis, a member of the large family Cryptophagidae, ‘found on flowers, chiefly broom and gorse’, which fits (photo 3). However, there are no records on National Biodiversity Network (NBN) north-west of the Great Glen (map 4). The second is a small rove beetle or staphylinid, which is well outside the scope of my competence, and will be referred to Stephen in due course.
The Norway spruce Picea abies yielded a larch ladybird Aphidecta obliterata, which is, unlike conventional ladybirds, pale brown and unspotted. There were two medium-sized weevils, a larger raspberry weevil Otiorhynchus singularis, a widespread relative of the notorious vine weevil O. sulcatus, and a smaller one, covered with round golden scales, Andrion regensteinense, which had strayed off the nearby gorse bushes.
There were also two other tiny beetles, which I was quite unable to identify using the keys in my ancient tome on British beetles (see below). In the end I discussed them over the telephone with Stephen and he was able to name them as the tooth-necked fungus beetle Laricobius erichsonii (photo 5), which is a relatively recent addition to the British fauna (first found in Suffolk in 1971). Our only member of the family Derodontidae, it is described as a ‘voracious predator of the harmful woolly aphids on firs’, and is steadily spreading across the British Isles. However, there are no records on NBN north of Inverness (map 6).
In addition to barkflies, there would appear to be enough local discoveries to be made amongst Assynt’s beetles to keep me occupied, whilst I still have the manual dexterity and visual acuity to mount and try to identify them, and help from friends when I get stuck.
P.S. The only comprehensive text for identifying the 4000+ species of British beetles was for many decades A Practical Handbook of British Beetles by Norman H. Joy (1932), in two volumes. It is only now being replaced by Beetles of Britain and Ireland by Andrew G. Duff, of which the first and fourth volumes (of four) have so far been published. There are also a number of profusely illustrated web-sites, which can help confirm identifications, including www.coleoptera.org.uk (UK Beetle Recording) and www.thewcg.org.uk (Watford Coleoptera Group).
Ian M. Evans