Hydrophilidae - Introduction
Many hydrophilid beetles (order Coleoptera), both adults and larvae, are aquatic or semiaquatic, but some live in fresh mammal dung, humus-rich soil, or decaying leaves. Generally, the adults of both the aquatic and terrestrial species are herbivorous, but will also eat dead animal tissue, and a few prey on other insects. All larvae are carnivorous. Aquatic species may be found living in quiet pools, quiet areas of lakes or streams having an abundance of vegetation, or in brackish water.
Hydrophilid beetles range in length from 1.0 to 40 mm. They have short antennae (often concealed) ending in a 4 segmented club and with the first segment enlarged and almost always more or less enclosing the following segment. Some genera have a distinctive keel present ventrally.