Nine genera and 30 species of Hydrobiini and 3 genera and 12 species of Hydrophilini were found in Wisconsin, including a new species of Laccobius. Life cycles of all species of lentic Hydrobiini were similar; adults overwinter in terrestrial habitats, return to aquatic sites in spring to mate, oviposit adjacent to these sites, and eventually die. The riparian larvae complete development, pupate, and emerge sometime during the summer depending on the species and habitat, and teneral adults disperse to suitable aquatic habitats. Adults enter overwintering sites in late summer or early autumn. Lotic species of Cymbiodyta have a similar life cycle, with larvae probably developing along stream banks. Other lotic species, Crenitis digesta, Hydrobius melaenus, and Sperchopsis tessellata, apparently are semivoltine with both larvae and adults overwintering along margins of streams. In Hydrophilini, life cycles of Hydrochara and Hydrophilus are the same as described above for lentic Hydrobiini, except larvae are aquatic, developing in lentic habitats. Life cycles of Tropisternus also differ in having aquatic larvae; they differ further in having adults that overwinter in aquatic habitats, especially streams, deep ponds, and lakes, which they enter in late summer and autumn. Tropisternus ellipticus is lotic, with larvae and adults inhabiting streams, and larvae completing development in mid-summer. Keys to species of adults are included along with information about each species, which includes distribution and abundance in Wisconsin, range in North America, habitat, life cycle, and notes on identification.
Hilsenhoff, William L.
"Aquatic Hydrophilidae and Hydraenidae of Wisconsin (Coleoptera). II. Distribution, Habitat, Life Cycle and Identification of Species of Hydrobiini and Hydrophilini (Hydrophiudae: Hydrophilinae),"
The Great Lakes Entomologist, vol 28
Available at: https://scholar.valpo.edu/tgle/vol28/iss2/1