Labidostomis tridentata (Linnaeus, 1758)
This Palaearctic-wide species occurs throughout Southern and Central Europe from Spain to Ukraine and the Balkans in the south and extending north into Denmark and the Baltic countries; it is locally common in southern and central regions but mostly very local and scarce in the north, it reaches to the Arctic Circle in Norway but there has been a drastic decline over recent decades and here, as well as in most of the Baltic countries, it is classed as highly endangered. In the UK it was formerly known from a few scattered sites in Southern and Central England but the most recent records are from Kent and East Sussex in the 1950s and the species is now very probably extinct here. Adults are active from May until July, they typically occur in open deciduous woodland with a good range of trees and herbaceous vegetation; they are diurnal and frequently fly to visit flowers and feed on tender young foliage. In northern Europe they generally occur on dry grassland, pasture, heathland and riverbanks on southern-facing slopes near to woodland. They often feed on Birch (Betula L.), Hazel (Corylus L.), willows (Salix L.) and Oak (Quercus L.) but have also been observed on other species and they sometimes move to herbaceous species such as docks (Rumex L.) to feed. They are sometimes quoted as being associated with various ants and while the adults sometimes occur near to ant nests there appears to be no specific association and larvae do not develop within the nests. Females attach batches of up to 25 eggs to leaves on long filaments and then cover them with excrement and debris, and larvae generally emerge from early July, after 4 or 5 weeks. Larvae cover themselves with secretions and debris; early instars feed on algae growing on trunks and logs but as they develop they move down to feed among litter or under stones, and this is probably where they pupate. The overwintering stage is unknown but the species is thought to be univoltine throughout the range.
Labidostomis tridentata 1
Labidostomis tridentata 2
6.0-8.5 mm. Very distinctive and not likely to be confused with any other UK species. Forebody and appendages dark metallic green or blue, elytra pale to dark brown. Head broad and flat or slightly depressed between large and convex eyes, finely and quite densely punctured throughout, antennae short and robust with segments 5-11 serrate. Pronotum transverse, broadest across acute (from above) and slightly raised posterior angles and narrowed to a rounded apical margin, basal margin bisinuate, surface uneven and roughly punctured throughout. Scutellum large, triangular and rounded or truncate apically and sculptured as the adjacent pronotum. Elytra slightly constricted in the basal third, otherwise smoothly curved from rounded shoulders to a continuous apical margin, surface randomly and moderately strongly punctured throughout, without striae but sometimes with vague longitudinal impressions. Middle and hind tibiae straight or weakly curved, front tibiae incurved apically. Tarsi pseudotetramerous with the third segment widely bilobed in both sexes. Males may be distinguished by their much broader front femora and longer front tibiae when compared with females.