Tachyporus nitidulus (Fabricius, 1781)
This must be one of the most widespread species within the subfamily; it is native to the western Palaearctic but has been transported with various products and is now established in many countries worldwide. In Europe it is locally common and often abundant throughout, including the Canary Islands, Azores and Madeira, extending to the far north of Scandinavia and Iceland, it occurs across North Africa and the Middle East and sporadically further south e.g. Ethiopia and Eritrea, it extends east through Russia, Afghanistan and Pakistan and is established in New Zealand and the Chatham Islands. In the New World it has only recently (2006) been recorded from Canada but has been long established in the United States where it occurs over much of the country and, of the 30 or so American species of the genus, is often the most abundant. Here it is generally common and often abundant throughout England and Wales including the Isle of Wight, Anglesey and Man, and further north there are a few records from eastern Scotland, the Western Isles and Orkney. It is a widely eurytopic species occurring from lowland to alpine-zone altitudes throughout its range; it often occurs in marginal or other permanently wet or damp habitats e.g. streams, marshes, sphagnum bogs and cliff seepages among decaying vegetation and accumulated leaf-litter but may also occur among decaying logs and stumps in any situation or under or among stored hay and straw. Adults occur year-round but are most abundant in late summer and autumn, during the summer they might occur by sweeping grassland or flowers, and they are sometimes common on umbel flowers, while in the autumn and winter they may be found among decaying fungi, grass tussocks or moss in wooded situations. At higher altitudes they occur in mammal nests and at higher latitudes also in beaver lodges. Adults may be brachypterous or fully-winged and so during the warmer months might be expected to occur in any situation including domestic gardens where they may become established in compost heaps etc.
A very small and rather variable species; when mature the head is very dark, often black, and the pronotum and elytra are testaceous throughout or with the area around the scutellum only a little darker and ill defined, the abdomen is usually darker then the elytra and each segment is broadly paler apically. With experience this species will be seen to be narrower and less convex than many others of the genus. Size varies widely as the abdominal segments tend to telescope together in set specimens but from the front margin of the head to the elytral apex they vary between 1.1 and 1.4mm and the elytral length is 0.7-0.8mm. Head triangular and broadly rounded anteriorly from above and with weakly convex eyes that are more-or-less continuous with the outline. Antennae long, slender and entirely pale; segments 1-6 elongate and only slightly widened towards the apex, 7-10 broader and widest near the apex and the terminal segment is long and constricted before a rounded apex. Maxillary palps darkened towards the apex, apical segment short and conical. Pronotum glabrous and shiny, transverse and broadest at or behind the middle, at the widest point a little wider than the elytra, anterior and posterior angles rounded but distinct, lateral margins with several long outstanding setae. Elytra slightly elongate, distinctly flattened and almost parallel-sided, the humeral angles are usually at least partly hidden beneath the pronotal margin and the apical margins are separately and only weakly curved. Abdomen generally darker than the elytra and often faintly iridescent, with numerous long setae along the raised lateral margins, punctation fine and rather dense throughout. Legs long and slender, mid and hind tibiae with several long setae along the outer and inner dorsal margins. Tarsi 5-segmented; basal segments of the front and middle tarsi weakly expanded in both sexes.