Tachyporus dispar (Paykull, 1789)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
TACHYPORINI MacLeay, 1825
Tachyporus Gravenhorst, 1802
Although described in the eighteenth century, this species was for many years largely ignored in the literature as it was widely considered to be conspecific with the very similar T. chrysomelinus (L, 1758), which is the type species of the genus. The present species is now considered distinct and there are several reliable morphological and genital features that allow straightforward identification. T. dispar is generally common throughout Europe, extending north to the UK, Denmark and above the Arctic Circle in Norway and Sweden, it is present on most of the Mediterranean and Atlantic islands but seems to be absent from North Africa. To the east it is widespread across Asia Minor and extends through Siberia and Mongolia to the far east of Russia, it was first recorded from North America in 1928 and has become widespread across the northern United States and parts of Canada. The species is generally common throughout most of this range and occurs from lowlands to subalpine altitudes. In the UK it is common and often abundant throughout England, Wales and southern Scotland, including all the islands, and more local and sporadic further north to the Scottish Highlands, the Outer Hebrides and across the north of Ireland. Typical habitats are dry grassland, open woodland and wasteland etc., they are often common in disturbed sites such as road verges, gardens and parkland and they may be abundant on arable land. Adults are present year-round, they overwinter among litter or in moss or tussocks in sheltered sites and are active from March until November although they often become active during mild winter spells. Reproduction occurs in spring and early summer and it is thought that only the adult stage overwinters. Adults and larvae are predaceous feeding on small insects and their early stages, especially various aphids, and are thought to contribute significantly to pest control in arable situations. They may occur in flood-refuse or extraction samples through the winter but otherwise they easily sampled by searching the ground among dense vegetation and they usually occur in numbers, they also climb stems in search of prey and so will regularly occur when sweeping. Specimens will need to be taken for critical examination as there are several very similar species which may occur together, especially in dry habitats.
3.5-4.0mm. Elongate and narrow (when the abdomen is extended), continuous in outline and tapered anteriorly and posteriorly, forebody glabrous (although with extremely fine pubescence visible only under high magnification) but for scattered 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 quadrate or nearly so and much longer than the pronotum, broadest across rounded shoulders and narrowed or parallel-sided to rounded or slight 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 four setae, including one on the inside of the posterior angle. This arrangement of four punctures along the apical margin is important as in the very similar T. chrysomelinus there are only three setae, 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 a tiny apical spur. 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 chrysomelinus by the form of the aedeagus; in the present species there is a long (0.25 mm) internal sclerite near the base while in chrysomelinus this is also present but it is much shorter. The aedeagal parameres in the present species are shorter and project less far beyond the apex of the median lobe when compared to chrysomelinus; this can be illustrated well but is often not so clear-cut when working with dissections.