The anterior edge of the scutellar shield is often abruptly elevated (except in Psephenidae and Cneoglossidae).

Larvae of Lutrochidae and Elmidae, as well as the limnichid genus Hyphalus, have anal gill tufts.

[3] Byrrhoids mainly occur in aquatic and semi-aquatic habitats, including rapid cool streams, underneath rocks and wood in flowing water, waterside vegetation and rocks, emergent vegetation in water, damp soil and sandy shorelines.

[5] Byrrhoids are generally herbivorous, feeding on algae, moss, liverworts, lichens or grass roots.

[2][10] Recent phylogenies have split out the grouping Dryopoidea, including Dryopidae, Elmidae, Limnichidae, Heteroceridae, Chelonariidae, Eulichadidae, Callirhipidae, Ptilodactylidae and the extinct family Mastigocoleidae,[11][12] with phylogenies finding the group more closely related to Elateroidea than to Byrhhidae.