Cossonus parallelepipedus (Herbst, 1795)
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POLYPHAGA Emery, 1886
CURCULIONOIDEA Latreille, 1802
COSSONINI Schönherr, 1825
Cossonus Clairville, 1798
This is one of the most widespread European members of the subfamily; it occurs from France to the west of Russia and from the Mediterranean north to the UK and the southern provinces of Fennoscandia, it is generally common in the south of this range but very local and sporadic in the north where in many areas it decreased due to forest exploitation and is thought to be in general decline. Here it is a local and generally scarce species of the English midlands and East Anglia, there are a few records from Kent and South Wales but beyond this it is mostly absent from the south. Adults occur year round and are usually associated with damp decaying wood of a range of broadleaf trees, often aspen, beech, oak, poplar and willow but also many others and in northern continental areas they sometimes occur in debris-filled hollows in spruce and fir trees. There may also be an association with fungi as our only experience with the species was a specimen extracted from a sample of Trametes taken from a decaying beech tree in south Herts. Adults are nocturnal, the typical habitats are damp woodland and wooded parkland where they are active from March until July or August although on the continent they are active continuously from early spring until the autumn, peaking in abundance from May to July, they may be found on the surface of fallen wood at night and have also been caught in Malaise traps but remain hidden under bark etc, by day. Larvae develop through the summer feeding on decaying moist wood and are sometimes found along with adults. Adults have occasionally been found alongside the closely similar C. linearis (Fabricius, 1775).
Species of Cossonus are distinguished among our fauna by the form of the front tibiae coupled with the following features; funiculus 7-segmented, scutellum clearly visible, rostrum dilated in the apical half and the third tarsomere is not obviously dilated and only slightly wider than the second. 4.3-6.6mm. Entirely shiny dark brown to black or (usually) with the elytra little paler, appendages brown, the antennae usually lighter than the legs. Head transverse with weakly convex eyes and finely punctured and simply convex vertex, frons and rostrum a little more strongly punctures, rostrum dilated and parallel-sided in the apical third; the anterior part of the scrobes being just visible from above. Antennae long and slender (for this subfamily at least), scape gradually broadened distally and almost as long as the rostrum, funicular segments becoming more transverse towards the apex and the club short and pointed, the sutures rather indistinct. Pronotum quadrate, broadest near the base and smoothly narrowed to a subapical constriction before a straight anterior margin, posterior angles widely rounded, disc slightly convex and with small discrete punctures that are about the same size at the base as those towards the apex. Elytra with broadly-rounded shoulders, parallel-sided to a continuously rounded apical margin and with impressed and regular-punctured striae which are distinctly narrower than the slightly convex interstices. Legs long and robust, femora unarmed, middle and hind tibiae curved along the inner margin, front tibiae smoothly curved throughout the length, outer apical margin of all tibiae produced into a sharp, hook-like process. Tarsi 5-segmented, basal segment elongate, second segment much less so, the third lobed apically but hardly wider than the second segment, at least partly enclosing the tiny fourth segment, apical segment long and slender. Claws smooth and not fused at the base.
Similar species
Cossonus linearis
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Generally smaller (4.4-5.1mm).
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Pronotum with large, in places confluent, punctures along the base.
