Clivina collaris (Herbst, 1784)
A widespread European species though generally more local and less common than C. fossor, it is absent from many northern areas e.g. Norway and Finland and very rare in others e.g. Sweden and Denmark, in central Europe it is common from lowland to boreal mountain altitudes, extending south to the Mediterranean but absent from North Africa. The distribution otherwise includes Asia Minor and extends east into Siberia, it is also adventive and long established in North America, having been first recorded in the 1830s. Here it is widespread though local and generally uncommon throughout England, Wales and southern Scotland and very rare further north, it is absent from Ireland and most of the islands. Adults occur year-round and are active from March until October, peaking in the spring and early summer when they breed, the new generation appears from late summer and will go on to overwinter. In general the species is more littoral than C. fossor, inhabiting wetland margins, fens, and riverbanks, usually on humus-rich clay or gravelly soil, although on the continent it is more eurytopic, also occurring in salt marshes, it can be common on cultivated soils and occurs in gardens and other disturbed sites. Adults may be sampled by pitfall trapping or turning stones and debris in suitable habitats; e.g. we found them by searching through flood refuse on an arable headland in North Somerset.
Very similar to C. fossor and once considered a variety of that species, C. collaris is consistently smaller, 5.0-6.0mm, slightly flatter and more rounded; when mature it is also bicoloured with the elytra paler than the forebody. Immature specimens of both species tend to be entirely pale and more or less entirely dark specimens of the present species do occur, here size is the best way to determine them. The terminal abdominal sternite also differs but this is comparative, in the present species it has strong granulate microsculpture and so appears dull whereas in C. fossor it is less strongly microsculptured. The sexes are very similar in C. collaris; in both the four setae on the last abdominal sternite are equidistant, and specimens will usually need to be dissected.