Polydrusus marginatus Stephens, 1831
This species is widely distributed through Europe from Spain to Romania in the south and north to the UK and southern Sweden, although it is absent from the northern Baltic countries and is very sporadic and generally rare throughout this range, it is also recorded from Turkey but has vanished from some of its former sites e.g. it was last recorded from Norway in 1896 and is now considered to be long extinct. In the UK it is very local in Southern and Central England although it tends to be common where it occurs. Typical habitats are open broadleaved woodland and wooded parkland where the adults frequent dry and sunny situations, in Europe they also occur non trees in open grassland and in conifer forests and it has been recorded as a pest in vineyards and orchards. Adults occur from April until August and have been recorded feeding on the foliage of range of trees including Hazel, Aspen, Alder, Oaks, Poplar, Ash, Cherry, Elm and willow, but locally we find them mostly on Birch foliage, they have also been recorded from Pine and Broom but these were probably adventitious. They are flightless and spend much of their time on the ground, ascending trees in warm weather to feed, we have extracted mating pairs from moss samples taken from Birch logs in April and swept pairs from Birch foliage in early May and June and so breeding extends over a long season, and typical of the group the larvae probably develop underground feeding on roots. Sweeping or beating foliage in warm weather may produce adults but they often occur in pitfall and flight-interception traps and we have repeatedly found them among extraction samples of moss, litter and even dry terrestrial fungi from our local Watford woodland and so by sampling foliage alone the species may well be missed. We have yet to find adults among winter extraction samples but, like many members of the genus, they are likely to be present in the autumn and overwinter at the pupation site, becoming active in the spring in response to increasing temperature or day length.
Polydrusus marginatus 1
Polydrusus marginatus 2
3.6-5.0 mm. Elongate, convex and discontinuous in outline, shiny black with dark to pale brown appendages, vestiture consists of weakly metallic pink or grey setae-like fine scales arranged transversely on the pronotum and longitudinally on the elytra. Head with convex and prominent eyes and long diverging temples that are as wide at the base as the pronotal apex, surface evenly convex and deeply and moderately strongly punctured, rostrum quadrate with lateral scrobes angled down in front of the eyes. Antennae inserted at the apex of the scrobes, scape short, curved and gradually thickened towards the apex, segments 2 & 3 elongate, 4-8 quadrate or slightly transverse and 9-11 form a broad and pointed club. Pronotum quadrate or slightly transverse, broadest a little behind the middle and narrowed to curved apical and basal margins. Elytra elongate with rounded shoulders and a continuous and acuminate apical margin, striae strongly punctured, interstices impunctate but finely transversely rugose. Male elytra narrow and sub-parallel, female elytra broadly dilated behind the middle. Legs finely pubescent throughout, femora toothed below, more strongly so in the male, tibiae slender with curved inner margins and expanded at the apex. Claws fused at the base – this will distinguish it from superficially similar species of Sitona Germar, 1817.