Tachyporus chrysomelinus (Linnaeus, 1758)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
TACHYPORINI MacLeay, 1825
Tachyporus Gravenhorst, 1802
This very widespread species is generally common from lowlands to alpine regions across Europe to Asia Minor, Kazakhstan, Turkmenistan, Mongolia and China to the Pacific coast of Russia and Japan (Hokkaido). The species is sometimes quoted as occurring in North America but this is uncertain and such records may be based on the very similar Tachyporus dispar (Paykull, 1789) which is an established introduction from Europe. But for the Iberian Peninsula and some western parts of the Balkans it is common and often abundant throughout Europe; it increases in abundance from the Mediterranean countries north to the Baltic coast and it extends north to beyond the Arctic Circle in Norway and Finland. In the UK is very common across England and Wales north as far north as York although apparently scarce in the West Country, it extends sporadically further north through Southern and Eastern Scotland to Orkney and there are scattered records from Northern Ireland. Typical habitats are open grassland and woodland, arable fields and other disturbed sites such as road verges, wasteland and gardens, often on heavy and damp soils and frequently on permanently damp floodplains, marshes and fens etc. Adults occur year round, they overwinter in the soil or among moss or tussocks and are active between March and November although they are often active during mild winter spells, and they peak in abundance during May and June. Both adults and larvae are diurnal predators, they hunt for small insects etc. on the ground and adults may also climb stems to do so, as such they are considered to add a significant contribution to pest control in arable areas. Adults often occur with T. dispar but on heavier soils and in damp situations the present species is usually more common. Specimens can be sampled from tussocks and litter etc. at any time but during the warmer months they will often appear when sweeping grassland and low vegetation and they sometimes occur in flight-interception traps.
3.3-4.0mm. Elongate, narrow and continuous in outline, broadest across the pronotum and tapered anteriorly and posteriorly. Forebody glabrous (although with extremely fine pubescence which is visible only under high magnification) but for scattered erect setae, elytra and abdomen very finely pubescent. Head black, pronotum orange or obscurely darkened, elytra pale to dark brown with the basal and lateral margins and the area below the scutellum darker, abdomen dark with pale narrow apical margins to the tergites, and often with a faint metallic sheen. Head large and broadly transverse, with relatively large eyes and rounded temples that form a smooth lateral margin, surface smoothly convex, without structure. Maxillary palps pale brown or yellow, terminal segment long and slender; longer than the width of the elongate penultimate segment. Antennae 11-segmented and filiform, gradually but only weakly broadened from the sixth segment, pale at the base and darkened from the fourth or fifth segment. Pronotum transverse, broadest in front of rounded posterior angles and curved to a narrow apical margin, surface evenly convex and without structure, lateral margins each with four erect setae which are about as long as the first antennomere. Elytra much longer than the pronotum, quadrate or nearly so, broadest across rounded shoulders and narrowed or parallel-sided to rounded or obscure posterior angles and separately curved apical margins. Elytral surface very finely microsculptured and punctured throughout and with various longer setae (some of which may be missing or broken-in which case the points of attachment are always visible); four on the disc (each pair in line, the outer pair more posteriad than the inner pair, and a single seta behind the middle near the suture, each lateral margin with four long setae, the third paired with a smaller one on the inside, and the apical margin with three setae, including one on the inside of the posterior angle. This arrangement of three setiferous punctures along the apical margin is important because in the very similar T. chrysomelinus there are four, these need to be looked for very carefully and often the only way to be sure is to lift an elytron under good lighting and high magnification. Abdomen strongly tapering from the base, all tergites bordered and with long lateral setae, surface evenly and very finely punctured across the centre. Legs long and slender, middle and hind tibiae with various stout erect setae and all tibiae with tiny apical spurs. Tarsi 5-segmented; middle and hind tarsi slender, basal segments of front tarsi expanded, more so in males. The habitus and elytral punctation is usually sufficient to identify the species but doubtful males can be separated from males of dispar by the form of the aedeagus; in the present species there is a short (0.15 mm) internal sclerite near the base while in dispar this is also present but it is much shorter. The aedeagal parameres in the present species are longer and project further beyond the apex of the median lobe when compared to those in dispar; this can be illustrated well but is often not so clear-cut when working with dissections.