Actocharis readingii Sharp, 1870
Until recently Actocharis Sharp, 1870 included only the widespread A. readingii Sharp, 1870 (=A. marina Fauvel, 1871) but two further species are now included; A. cassandrensis Assing, 1992, from Greece, and A. calabrica Assing, 2004 from Italy. A. readingii has been recorded from coastal sites in the UK, France including Corsica, Italy including Sardinia and Sicily, Croatia, Malta and Algeria. In the UK it is widespread around the coasts of Devon and Cornwall; it was recorded from Scilly in 1970 and has recently been recorded from Pembrokeshire. In Mediterranean regions it usually occurs in the upper intertidal zone on sandy beaches while in the UK it is more typical of stony or rocky coastlines. Adults usually occur on the underside of rocks or among large stones in the intertidal zone, they have been recorded in all months from March until October but nothing is known of the biology. Because of the species very small size and cryptic colour and habits it is likely to be under-recorded; it has long been known from the West Country and it is considered to be very local-the same few sites having been worked by collectors over the years- but adults usually occur in numbers and, as they are flightless, there are probably many overlooked populations between the known sites. Turning stones or rocks on sandy or gravelly beaches is the best way to find the beetles but they must be looked for very carefully; they will appear either on the exposed surface of the stones or on the surface of water as it fills the exposed cavities.
1.4-1.7 mm. Elongate, parallel-sided and discontinuous in outline, dorsal surface finely pubescent and extremely finely punctured throughout. Body pale brown sandy, often with the head and/or pronotum darker, and with at least some tergites (usually 3.5) very dark grey or black, appendages pale or with the antennae and palps darkened apically. Head quadrate or slightly elongate, broadest towards the base and narrowed from rounded temples to weakly convex eyes that are only narrowly visible from above, basal margin flat, surface without structure and cheeks strongly narrowed anteriorly. Antennae 11-segmented and at least as long as the head and pronotum combined, segments 7-10 distinctly transverse and segment 11long and pointed. Pronotum quadrate, broadest behind perpendicular or slightly obtuse anterior angles and narrowed to rounded posterior angles, basal margin weakly sinuate and apical margin sinuate and produced medially, surface flat and without structure. Scutellum large and triangular. Elytra quadrate, about as long as or slightly shorter than the pronotum and curved laterally from rounded shoulders to perpendicular posterior angles, basal margins straight and converging to the suture, surface without striae. Abdomen parallel-sided or only weakly dilated apically, segments 1-4 impressed across the base and strongly bordered laterally, segment 5 strongly recurved apically. Legs short with simple femora that are widely visible in normal setting. Apical half of front tibiae with numerous short spines externally and a single fine terminal spur. Middle and hind tibiae with a few very short setae along the external margins and without apical spurs. Tarsi 4-4-5. Front tarsi weakly lobed and with the terminal segment robust, middle and hind tarsomeres more strongly lobed and with smaller apical segments.