Micropeplus staphylinoides (Marsham, 1802)
This is the most widespread and common of our UK species; with the exception of the West Country it occurs throughout England, Wales and the east of Scotland and there are records from Anglesey, Man, Orkney and the western Scottish Isles, in the south it is generally common but further north more local and sporadic. On the continent it occurs across North Africa and throughout Europe north to the Netherlands and east to Turkey but it is very local generally rare, especially in the north of its range e.g. it is listed from Poland on the strength of a single record. Adults occur throughout the year, the usual habitat is among decaying vegetation and leaf-litter in damp or wet situations, often near woodland or wetlands but they also occur in open damp grassland and are sometimes common among straw and hay left in fields to dry. Compared with other members of the genus they are more eurytopic; they have been found under decaying bark and logs and may be swept from grassland or on arable borders, they have been recorded swarming in flight over decaying bales of hay and dung, and locally most of our records have been from extraction samples of oyster mushrooms fruiting in shrub beds in local parks. On the continent they are also synanthropic, occurring in barns and sheds where crops or silage is stored and in the south of the range they are often found on walls and fences during the summer. Adults disperse by flight in the evening and are attracted to light. A description of the larva was provided as early as 1868 by Sir John Lubbock, see HERE.
2.0mm. This species is readily recognized by the form of the penultimate abdominal tergite which, when viewed from the side, is produced into a backward-facing tooth over the declivity. Black with pale pronotal margins and appendages, forebody rather dull, elytra and abdomen shinier. Head transverse with convex and large-faceted eyes and short temples that are usually concealed by the pronotum, vertex with two anteriorly-converging longitudinal furrows flanked by a depressed round or triangular area extending to the base. Clypeus strongly microsculptured, rounded or obscurely angled in the female, produced forward in the male. Pronotum strongly microsculptured; transverse with curved lateral margins and strongly-produced anterior angles, disc with a complete longitudinal ridge either side of the middle, sometimes joined near the middle, and other incomplete ridges delimiting depressed areas and a central deep fovea, laterally widely explanate. Elytra transverse and much narrower across the base than the pronotum across the posterior angles; each with 4 longitudinal ridges (including the sutural), the cuticle between smooth and shiny between very strong punctures that form two or three rather randomly arranged rows. Abdomen dilated compared with the elytra, each tergite with three strong longitudinal ridges and a weaker ridge delimiting the lateral border, on the penultimate tergite the median ridge is produced (as above) and the lateral ridges incomplete. Legs short and slender, the femora narrowly visible from above, tibiae long and weakly curved; each with two rows of fine setae along the dorsal surface, tarsi 4-segmented with the terminal segment much longer than the others combined.