Coelostoma orbiculare (Fabricius, 1775)

This species is generally common throughout the Palaearctic region from Europe to the far east of Russia and Japan and has recently been recorded from Canada (Ontario); in Europe it is common from lowlands to about 1800 m and extends from the Mediterranean to the UK and far above the Arctic Circle in Fennoscandia, it is present on many of the Mediterranean islands but absent from North Africa. In the UK it is common throughout England and Wales and rather less so across Scotland and Ireland, and with the exception of Orkney and Shetland occurs on all the islands. Typical habitats are well-vegetated margins of stagnant ponds and ditches, they often common among wet reed bed margins and peaty moorland ponds, we have found them under debris in salt marshes in Hampshire and specimens are often present among numbers of other hydrophilids in temporary pools in the spring. Adults usually occur among silty or peaty soil or matted vegetation and moss in shallow marginal situations but they are also common among floating masses of leaves and moss, they are diurnal as well as nocturnal and often come to light in the summer. Breeding occurs in the spring and larvae develop through the summer in marginal situations, they have been sieved from wetland litter samples and presumably inhabit permanently wet litter etc., pupation occurs late in the summer and the resulting adults will go on the overwinter among litter etc. Adults occur year-round; they peak in abundance during late spring and early summer and remain active into the autumn but are rarely found in numbers, they are easily sampled through the season by sweeping among marginal vegetation, and through the winter may be found among litter samples or flood refuse.