Hydrophilidae

Hydrophilidae, the water scavenger beetles, are a family of aquatic beetles in the order Coleoptera, superfamily Hydrophiloidea. They include about 2,000 described species in many genera and are found worldwide, especially in warm temperate to tropical regions. Adults are typically oval or elongated; the dorsum is smooth and often dark. The head is often tucked under the thorax. Antennae are short and clubbed; maxillary palps are long and conspicuous, sometimes extending beyond the head. Hind legs are flattened for swimming.

They inhabit still or slow-moving freshwater, including ponds, marshes, and ditches. Diet is variable: detritus, decaying vegetation, algae, and in some species small invertebrates; many are scavengers or omnivores. Both adults and many larvae are aquatic; larvae are usually predatory. Hydrophilids carry a bubble of air when submerged, enabling respiration at depth. Reproduction: eggs laid near water; larvae undergo several molts before pupation, with complete metamorphosis.

Hydrophilidae belong to Hydrophiloidea and include several subfamilies, such as Hydrophilinae and Sphaeridiinae. They are cosmopolitan but most diverse in warmer regions. They serve as indicators of freshwater health and are used in ecological studies; some species are kept in educational aquaria. Threats include habitat loss and pollution of freshwater systems.