Many species are predacious, some with extra-oral digestion. Species from secondarily aquatic families often feed on aquatic vascular plants. Communities Coleoptera species are present in streams of all sizes as well as all types of shallow lentic habitats. The larvae and adults of most species are dependent on atmospheric oxygen, but some respire aquatically or obtain oxygen from submerged vascular plants. Beetle communities are most complex in small, warm, ponds, where the many species are separated by habitat, trophic role, period of activity, and body size.
Temporary ponds are often well populated.
The open channel of lotic habitats normally has few species, but may have large densities. The beach zone of both lentic and lotic waters may have many specialized species. Adults and larvae normally have the same habitat, but there are notable exceptions. Aquatic species are far less consequential to man. Some are eaten by fish, others may eat fish, may help control nuisance organisms, many are good water quality indicators.