Bostrichus capucinus (Linnaeus, 1758)
Capuchin Beetle
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POLYPHAGA Emery, 1886
BOSTRICHOIDEA Latreille, 1802
BOSTRICHINAE Latreille, 1802
BOSTRICHUS Geoffroy, 1762
This is a very widespread though sporadic and local species throughout much of Europe extending north to Scandinavia and the U.K., although here it has not been recorded in the wild since the early twentieth century, and across Mediterranean North Africa and Asia Minor, east through Russia, Kazakhstan (etc.) to Mongolia, China and eastern Siberia. It is present on most of the Mediterranean islands and is regularly recorded around the world from European and Asian timber exports; it has been found many times in the United States but so far has failed to become established. Whether it has been established in recent times in the U.K. is doubtful as there are only very few records and it was not mentioned in Joy’s Handbook. Adults occur from April or May until July or sometimes a little later, the typical habitat is open and dry woodland, scrub and wooded parkland etc. with plenty of fallen timber, and in continental Europe they are occasional pests of stored or structural timber and furniture etc., they are primarily associated with various oaks; Quercus robor, Q. ilex, and Q. toza (Pyrenean oak) but have been recorded from a wide range of broadleaved shrubs as well as bamboo and pine. Adults are mostly nocturnal but will occasionally swarm on very hot days and sometimes in large numbers. Both sexes bore into wood, leaving round entrance holes, where they construct a circular breeding chamber which they keep clear of frass and in which they mate. Females lay eggs in crevices or pores in the xylem, mostly on dry fallen timber devoid of bark but also on standing trunks, and larvae develop just below the surface, boring through the wood and reducing it to a fine dust. They overwinter and pupate in a cell near the surface during the spring, the adults emerging through circular exit holes between three and four mm in diameter. The larvae are C-shaped, white or pale grey with a small and well-sclerotized head which is darker, the thorax is massively expanded and the abdominal segments have latero-ventral folds, the basal three or four with groups of stiff setae on the folds. The apex is simply rounded, unmodified and without processes.
Adults vary widely in size from 7.5 to 16mm in length and from 2.5-5.5mm in width. This is a very distinctive species due to the colouration, entirely black with the abdomen and elytra red, and the characteristically shaped and sculptured pronotum. Occasionally the elytra are brown rather than red and very rarely they may be almost black. The forebody has rather dense black and semi-erect pubescence. Head hypognathous, but often extended forwards in set specimens, and narrowed in front of weakly convex and relatively small oval eyes; coarsely and confluently punctured and often with a distinct longitudinal groove along the vertex. Antennae widely separated, inserted well in front of the eyes and above the base of the mandibles; 11-segmented, the two basal segments much larger than 3-8, and 9-11 form a loose club, entirely black or variously pale towards the base. Pronotum very convex, obliquely angled above in side view, the anterior face with dense tooth- or rasp-like tubercles, the posterior half densely but much less strongly sculptured. Lateral margins from above evenly rounded from obscure anterior angles to obtusely-rounded posterior angles, dorsal and ventral surfaces poorly delimited due to the surface structure. Prosternum short in front of oval and more or less contiguous coxal cavities, densely tuberculate throughout. Scutellum black and densely punctured. Elytra long and weakly expanded towards the apex, entirely covering the abdomen and continuously rounded apically. Surface shiny and glabrous or with very fine pale-brown hairs, with very strong and random punctation which may sometimes form obscure longitudinal lines, sometimes there are raised and flattened costae among these, and there are usually much finer punctures scattered among the larger ones. Lateral margins sinuate and weakly explanate towards the apex. Legs long and slender, entirely black but for the tarsal extremities and claws which are variously red. The male has long pale-brown hairs below the posterior tarsi.