Rugilus subtilis (Erichson, 1840)

This Western Palaearctic species is widespread in Southern and Central Europe, extending north into the Netherlands, UK, Germany and Poland and west into parts of European Russia, to the south it reaches Greece and Turkey and a few sites in north-eastern Spain represent the western limit of the distribution. Throughout most of the range it is very local and scarce; in the UK it is known from a few sites in Kent and Sussex and there are a very few scattered records from the midlands and East Anglia. Here it is often associated with chalk grassland but on the continent it occurs more widely, on open grassland and arable land, damp meadows and woodland, clay and limestone pits as well as wetlands, river margins and ditches etc., it is a mostly lowland species but has been recorded up to 1300m in Turkey. Adults probably occur year-round; they are active from March until October although most records are from the spring and they are only rarely recorded during the summer. They occur among matted vegetation, under debris or among moss and plant roots and specimens have been recorded from a hollow willow trunk on the continent, they rarely seem to be active in the open and are usually recorded by sieving suitable material although they occasionally occur in pitfall traps.

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​5.6 mm. Body very finely pubescent, rather shiny black or with the elytra reddish towards the apex, mouthparts reddish but for the penultimate maxillary palpomere which is partly darkened, antennae red, legs reddish-brown, usually with the femora darkened apically. Head quadrate with small and weakly convex eyes and continuously-rounded temples, surface densely punctured throughout, confluently so towards the margins and smoothly curved anteriorly, labrum with two small teeth and a median notch. Mandibles long, curved and sharply pointed, internally with strong teeth in the basal two-thirds, three on the left mandible and four on the right. Antennae placed on tubercles in front of the cheeks and outside the margin of the mandibles, 11-segmented with the basal segment the longest and subsequent segments progressively shorter to a pointed terminal segment. Pronotum elongate and distinctly narrower than the head, broadest along a short and almost straight lateral margin and angled to a narrow neck and straight basal margin, surface densely and confluently punctured but for a narrow central strip which is often confined to the basal half. Elytra weakly curved laterally from rounded shoulders to separately recurved apical margins, sutural border depressed, often with a longitudinal sub-lateral depression, otherwise smooth and finely but not densely punctured throughout. Basal abdominal tergites densely punctured, more strongly so across the weakly depressed base, apical tergites more finely and sparsely punctured throughout. Sub-apical abdominal sternite with a strong median notch in males, smoothly curved in females. Legs long and slender, femora unarmed, front tibiae weakly sinuate internally, middle and hind tibiae smooth and hardly broadened from the base. Tarsi 5-segmented and simple; the front tarsi at most only slightly broader than the others. Claws smooth and appendiculate.