THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands
An Identification Guide and Educational Resource

Sciomyzid larvae tend to live in freshwater marshes, and along the edges of ponds, lakes, and streams, among vegetation and floating debris. They are almost exclusive to wetland habitats and still waters, and prey on snail eggs and snails, sometimes taking days to kill their prey. Marsh flies may even pupate in snail shells or lay their eggs on the surface of the shell.

Like several other fly larvae, marsh flies have a tubular body without a well defined head capsule. The abdominal segments are encircled with a ring of bumps. Their abdomen narrows, then ends bluntly (not indented) with several small lobes around the edges.

The images above are used with permission from Dan Pickard with the California Department of Fish and Game.