Fossilized Water Pennies (Coleoptera: Psephenidae) in the Middle Pleistocene Lake Deposits in Shiobara Site,Tochigi Prefecture, Japan

摘要

The Middle Pleistocene lake deposits in Shiobara yield abundant animal and plant fossils. Three specimens of Psephenidae larvae were newly discovered, and identified as Ectopria opaca (Kiesenwetter, 1874) and an indeterminate genus of the Psepheninae.The former is the first fossil record of the species. The latter is probably Malacopsephenoides japonicus (Masuda, 1935) whose fossilized pupa was reported from the same site previously. These larvae are lotic species, suggesting the existence of rivers. However, as lotic species inhabit modern lakes (e.g., Lake Biwa in Honshu), Psephenidae larvae were also presumed to have inhabited lakes and the remains were preserved in the deposits.