Enicmus histrio Joy & Tomlin, 1910
Thought to be native to the western Palaearctic region this species now occurs throughout Asia to the far east of Russia, China and Japan, and extends south into India and across Asia Minor, it is also established in North America though so far restricted to Newfoundland and Nova Scotia, having been first recorded in 1996, and there have been occasional records from many countries worldwide. It is locally common throughout Europe and North Africa, extending north to the UK and northern Fennoscandia and occurring from lowlands to about 2200m in the Alps. It is locally common though probably under-recorded throughout England and Wales including Anglesey, Man and the Isle of Wight but generally absent from Scotland except for the extreme south. Adults occur among decaying vegetable matter in a wide variety of both wet and permanently damp habitats; among leaf and reed-litter in wetland marginal situations, among decaying wood and bark of various deciduous trees and fallen timber, in moss and decaying cut grass, compost, mouldy hay and straw and among old decaying fungus, they are also synanthropic and have been recorded in houses and among stored wheat. Both adults and larvae are believed to feed on slime moulds (Eumycetozoa) and the spores of Myxomycete fungi, and this would explain the their widespread and general occurrence, adults occur year-round, they occur generally from spring to autumn and occasionally through the winter in suitable extraction samples, they have been observed mating in August but otherwise little is known of their life-cycle. Adults occur by general sweeping in grassland, searching under bark or sieving leaf-litter etc, and may occasionally be found on the surface of wood at night.
1.5-2.0mm. Body and appendages entirely brown, often with the forebody or areas of the pronotum and elytra darker, dorsal surface glabrous although at high magnification very short setae will be seen in the elytral punctures. Distinctive among our fauna by the form of the pronotum which is much narrower than the elytra, and the prosternal process which is keeled between the front coxae. Head slightly transverse with large convex eyes and long, near-parallel temples which are slightly obtusely angled and then strongly constricted to a short neck which is usually retracted into the thorax, surface strongly and densely punctured and usually without sculpture although in some specimens the clypeus is longitudinally weakly impressed. Cheeks long and parallel and produced forward, the head in front of the eyes much narrower than across the temples, anterior margin of labrum rounded, antennae inserted laterally ay the anterior clypeal angle, 11-segmented, the basal segment much larger than the others and the last three forming a gradual and loose club. Pronotum curved and widest in front of the middle and almost parallel-sided towards the base, lateral margin finely denticulate, anterior margin almost straight between protruding anterior angles, surface strongly and densely punctured throughout, widely explanate and with a transverse impression across the base. Elytra with regular and strongly punctured striae which are a little broader than the convex interstices, surface evenly convex (not transversely impressed across the base), humeri convex and produced forward and lateral margins smoothly curved to a continuously rounded apical margin, explanate margin variable but usually widest in front of the middle and absent in the apical third. Legs long and slender; femora narrow and simple, tibiae narrow, smooth and without apical spines. Terminal segment of all tarsi long and curved.