Cis boleti (Scopoli, 1763)
While restricted in range this is often among the commonest of the European members of the genus, the distribution is mainly central with isolated populations occurring north to the UK and in Fennoscandia to high above the Arctic Circle, to the south it occurs mostly in mountainous regions and does not reach the Mediterranean coast, more widely it occurs generally across the Palaearctic region to the far east of Russia and Japan. In the UK it is widespread and generally common across England and Wales, becoming more local further north to the Scottish border, it is generally absent from much of Scotland but there are a few scattered records from the northern Highlands. The species is associated with a range of fungal fruiting bodies on decaying broadleaf trees and fallen timber, e.g. various species of Polyporus P. Michell ex Adans. (1763), Daedalea Pers. (1801) and Lenzites Fr. (1838) but there may be a more specific association with various Trametes (L.) Fr. (1838), especially T. gibbosa (Pers.)Fr. (1836) and T. versicolor (L.) Lloyd (1920) as females have been demonstrated to react strongly to volatiles released during their decay (and here they are known to be enantiomer specific); early colonizing females will damage the fungi so causing it to decay and release volatiles which will attract more beetles and accelerate the fungal decay, other ciids e.g. Octotemnus may initiate the decay process and lead to the present species arriving, and the nature of the volatiles may indicate to females the likelihood of the fungus being a suitable host medium for oviposition. Males respond to a wider range of volatiles (or, in this case, enantiomers) and maybe only at higher concentrations. Once damaged a fungus is very likely to attract a large and varied population of beetles (etc.) which will quickly begin to consume or bore into it causing extensive physical damage before they mate and oviposit and this obviously reduces reproductive fitness of the fungus, C. boleti along has been shown to reduce this by up to 30% while in company with Octotemnus this mat increase to 64% 2. Adults occur throughout the year, they overwinter among fungi or under bark etc. and may be active during mild spells, they become generally active early in the spring and are soon abundant, usually among or around fungi but they might also occur in large
numbers under the bark of decaying stumps etc. with no obvious fungal association. They mate and lay eggs within decaying fungi from spring onwards and larvae tunnel through the tissue, feeding as they go; they are mobile and may move between fungi as fresh substrate becomes available. Larval development is rapid and pupation occurs within fungal tissue, they are able to tolerate a wide range of conditions and may occur in old specimens repeatedly soaked by rain or among very dry and brittle tissue sheltered from the weather. Where breeding populations occur they are usually accompanied by Octotemnus which is almost always the first to colonize new material, the two species therefore usually occur together in numbers but as the host material dried out with age Octotemnus leaves and boleti is usually the only ciid present. Adults will occur among suitable extraction samples throughout the year, they may be sampled from dead and decaying wood or, most interestingly, may searched for at night when they may occasionally be found active on the host material. We once found dozens of specimens under the bark and among the wood of a small (about 100mm in diameter) Prunus stump which was regularly passed over by lawnmowers in our local park, there was no obvious fungal association but the beetles kept arriving and becoming more abundant over a few weeks during June 2008, it was not obvious why, with abundant decaying wood nearby, but this site was very attractive to the beetles.
Although variable this is generally the largest of our UK ciids at 2.4-4.0mm, the colour varies between pale and dark brown, almost black and the surface sculpture is rather variable and so specimens will need to be examined carefully for a certain identification. Elongate-oval, near parallel-sided and very convex; the dorsal surface with very fine, almost scale-like pale pubescence. Head transverse and mostly hidden within the thorax, with relatively large and weakly convex eyes and 11-segmented antennae; male clypeus with a blunt tooth either side of an emarginate median area, female smoothly curved. Pronotum transverse and extended anteriorly to form a short and flat ‘hood’ over the head, explanate lateral margins wide and visible from above for their entire length, basal margin not bordered; this must be looked for very carefully by tilting the specimen through various angles. Surface finely and densely punctured and with deep irregular impressions across the disc. Lateral margins of the pronotum and elytra with tiny erect scales which are visible at X40 but often missing in places. Scutellum relatively large, triangular and punctured as the pronotum. Elytra with prominent shoulders and continuously rounded apically, with very fine punctures throughout as well as much larger punctures that are arranged, sometimes loosely so, into rows. Legs short and robust; femora only narrowly visible from above, middle and hind tibiae evenly and weakly broadened to a simply truncate apex, front tibia sinuate and produced into an external apical tooth.