The beetles of the genus Donacia, are members of the leaf-eating Chrysomelidae) family and no real waterbeetles, though their way of life is bound to the water. In Europe there are about 20 species, mostly living on their own specific food plant. This one was sitting on a leaf of floating pondweed, but of course this may have been a coincidence. The species of the Donaciinae subfamily are sometimes called reedbeetles, because the passing fishermen and other observers mark them mostly when sitting in groups on reed stems. The large antenna make them look a bit like long horned beetles.

The white, grub-like larvae of these beetles are real water animals: they live in the mud of the bottom on the roots of water plants, from which they suck sap and air. They never come to the surface. In the end they pupate, the pupa cemented to the same roots the larva lived on. On the picture at left a pupa that has been taken from a root. The size is about 7 millimeters. When the beetle is ready, it climbs above the water.