Tachinus subterraneus (Linnaeus, 1758)
This widespread and locally common species occurs throughout the Palaearctic region and is now established in North America following introductions from Europe; it is present throughout Europe with the exception of the far north and occurs from lowlands to the subalpine zone. In the UK it is common across Wales and England north to Nottingham, rather less so further north as far as Glasgow and there are scattered records from the Scottish Highlands. Adults are present year-round although rarely seen during the warmer summer months; they peak in abundance during spring and autumn and are generally active through the autumn and winter. The species is widely eurytopic; it is often recorded from deciduous and coniferous woodland, hedgerows and wooded parkland and pasture but it also occurs in disturbed habitats including urban gardens and verges, and is sometimes recorded at light and sap. Both adults and larvae are predaceous, feeding mostly on Diptera larvae and small insects; larvae are known to develop through the winter among decaying vegetation and have been found in numbers in domestic compost heaps etc., fully grown larvae have been found in small cells in the earth beneath compost heaps during the winter and this is presumably where they pupate as pupation has been observed under artificial conditions during January. Adults have been found through the winter in decaying fungi and among rotting wood etc., and on the continent from bat droppings in caves, among horse droppings and in underground mammal nests, they become common in the spring but are infrequently seen during the warmer months, a further peak in numbers might suggest a summer brood but it is more likely that adults diapause from early summer and do not breed until the autumn or winter.
Tachinus subterraneus 1
5-6.5 mm. Elongate with long elytra and a distinctly tapering abdomen, body shiny black but for the variably pale pronotal margins and a long and usually abrupt reddish marking below the elytral humeri, in some specimens the apical margins of the abdominal tergites are narrowly reddish, legs pale to dark brown, antennae dark with several pale basal segments. In very rare examples, sometimes referred to as ab. bicolour Gravenhorst, 1806, the pale markings are expanded so that only the head, the centre of the pronotum, the elytral margins and basal abdominal tergites remain black. Head and pronotum with finely impressed cellular microsculpture between very fine punctures, the surface often finely wrinkled, elytral sculpture similar but the microsculpture is often doubled and the punctures more widely separated, abdomen very finely punctured and pubescent throughout and with fine transverse microsculpture. Head transverse and widest across convex and prominent eyes, temples short and weakly converging, anteriorly produced and smoothly curved in front of the eyes, surface smoothly convex but for an arcuate impression between the eyes. Apical maxillary palpomere long and tapering, penultimate segment shorter and broader, antennae pubescent from the fifth segment, gradually and only weakly broadened towards the apex. Pronotum transverse, broadest in the basal half and smoothly rounded laterally, surface smoothly convex and without structure. Scutellum transverse and more-or-less smoothly rounded, surface finely punctured and with dense transverse microsculpture. Elytra elongate, slightly narrower across the base than the base of the pronotum, and widened to rounded posterior angles, surface without striae and the sutural margin simple, not overlapping or raised. Abdomen strongly bordered and gradually narrowed, only the large penultimate tergite with several long lateral setae, surface as described above but the basal tergites have two small patches of dense yellowish pubescence which become obvious in strong light. Legs long and narrow, the middle and hind tibiae with four groups of stout setae, front tibiae expanded and with shorter spines towards the apex. Tarsi five-segmented, middle and hind tarsi simple, basal segments of front tarsi expanded, especially so in males.