Aplocnemus impressus (Marsham, 1802)
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POLYPHAGA Emery, 1886
CLEROIDEA Latreille, 1802
RHADALINAE LeConte, 1867
Aplocnemus Stephens, 1830
Widely distributed throughout southern and central Europe, reaching east through Ukraine to western parts of Russia and north to the UK and southern provinces of Sweden and Finland although it is absent from some of the southern Baltic countries, it is local and rather uncommon in the south and sporadic and generally rare further north. The UK distribution is restricted to a few sites in Sussex and Kent, and a series of sites in the midlands from the Severn catchment area, although it was formerly more widespread in the south. The species is saproxylic, in the UK occurring on various deciduous trees such as sycamore birch and, especially, oak as well as occasionally pine but on the continent it is recorded from other conifers, especially Norway spruce (Picea abies (L.)) Typical habitats are open established deciduous and mixed woodland or wooded parkland with plenty of trees in various stages of decay, although in northern Europe it is more usually associated with old conifer forests. Adults appear from April and persist into the summer; they frequently visit conifer or broadleaved-tree flowers and otherwise spend their time low down on trunks or fallen timber. Mating occurs early in the season and larvae develop under bark where they predate early stages of other sub-cortical insects, especially those of bark beetles. Fully-grown larvae pupate under bark or in old cones, adult beetles eclose in the autumn and most will remain in situ until the following spring but they have been found overwintering among bark and moss at the base of conifer trunks in northern Europe. Sampling is usually by inspecting likely fallen timber in warm weather when the adults are likely to be basking, otherwise they might be swept from flowers or appear among likely extraction samples taken during the colder months.
4-5 mm. Elongate-oval and discontinuous in outline, dorsal surface moderately strongly punctured, with mostly erect setae on the pronotum and recumbent pubescence to the elytra, dark grey with a metallic bronze or greenish reflection, the forebody sometimes with a contrasting lustre to the elytra, legs substantially pale but with darker areas to the tibiae and tarsi, antennae dark with the second and third segments, and often the apex of the basal segment pale. Head hypognathous and only narrowly visible from above, evenly convex, with protruding convex eyes and short converging temples, terminal maxillary palpomere elongate and fusiform, Antennae inserted laterally in front of the eyes, 11-segmented; three basal segments elongate, serrate from the fourth segment and similar in both sexes. Pronotum broadest at rounded posterior angles and narrowed to a rounded (from above) apical margin, surface evenly convex and without sculpture. Elytra with rounded shoulders and slightly dilated before a continuously rounded apical margin, lateral margin sinuate medially and finely toothed throughout, these are most obvious towards the apex, surface between the larger punctures smooth, without microsculpture or obvious fine punctures. Tibiae slender, slightly sinuate and with tiny apical spurs. Tarsi 5-segmented, the basal segments weakly lobed and the terminal segment long and expanded apically. Claws smooth and without an obvious basal tooth, at the base of each there is a long and broad membrane which is obvious in fresh specimens but soon shrinks and resembles an long appendage beneath each claw – this feature will distinguish the present genus from superficially similar species of Dasytes Paykull, 1799.