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Grooved Diving Beetle Acilius sulcatus

This species is called the Grooved Diving Beetle. The name is rather misleading, for only the female has grooved shields. In the grooves we find a lot of hairs. The meaning of this is to offer a hold to the male during mating. The male thus doesn't need the discs on the front legs of e.g. the Water Tiger. The male himself has smooth shields and often is difficult to identify, looking like a number of other diving beetles. It is a rather small species, reaching some 16 to 18 mm, not able to bite humans dreadfully. The larvae are not very big either and easily identifiable by their relatively long neck. They do not hunt big prey, but go for small animals, such as Water Fleas. The beetle overwinters in water. Until the water freezes over it remains rather active.

The Grooved Diving Beetle is also known as the Lesser Diving Beetle.