Alosterna tabacicolor (De Geer, 1775)
POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
LEPTURINAE Latreille, 1802
LEPTURINI Latreille, 1802
ALOSTERNA Mulsant, 1863
Alosterna Mulsant, 1863 includes 6 Palaearctic species and is most diverse in the east, the type species, A. tabacicolor, is generally common throughout much of northern Asia and Europe, extending north into Southern Scandinavia and the U.K. Here it is common throughout England and Wales, and there are a few Scottish records extending north to the highlands. The typical habitat is open woodland and wooded parkland. Adults occur from April to August; they fly well and visit a range of flowers including Ranunculus, Rosa, Aruncus and various apiaceae, generally in wooded situations but sometimes beside parkland pathways etc. remote from trees. Beating Crataegus as it comes into blossom in early May will often produce adults in numbers and a little later in May they can be found mating on flowerheads of all kinds. Host plants include a range of deciduous trees but the most frequent is oak and there have been occasional records from Pine. Larvae develop through the summer in damp decaying twigs and small branches, producing narrow irregular galleries which often extend into the xylem. The fully-grown larvae pupate in galleries under the bark during April or May and adults eclose soon afterwards, emerging from the wood during warm spells.
6-9.5mm. Elongate and slender, with the head and pronotum black and the elytra pale testaceous. The head is proportionally large with distinct rounded temples and eyes that curve around the antennal insertions, the vertex and frons punctured and pubescent and with a shallow longitudinal groove. Antennae entirely pubescent, black with various basal segments pale, the third slightly longer than the fourth. In the male the antennae reach the elytral apex, in the female they are shorter. Pronotum elongate, broadest in front of the middle and sinuate laterally to sharply acute posterior angles, without lateral borders and grooved longitudinally towards the base, otherwise smooth. Elytra testaceous with the sutural and lateral margins variously darkened, the surface moderately strongly and densely punctured and with pale recumbent pubescence, sub-parallel to evenly rounded or weakly truncate apices. Sutural margin raised, otherwise without any trace of striae or ridges. Legs long and slender, pale testaceous with the femoral apices and tarsi often darkened, sometimes the tarsi are entirely black and, rarely, the entire legs are black.
Alosterna is readily recognized in the field by its small size, colour and slender form but care must be taken to distinguish it from the similar-sized but more robust Pseudovadonia livida (Fabricius, 1777); in Alosterna the posterior pronotal angles are acute and produced whereas in Pseudovadonia they are perpendicular.