THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

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

Elmidae are an abundant, diverse, and ecologically important group of macroinvertebrates. As their name implies, elmids are commonly found in the riffles of flowing streams, but they have been collected from still water habitats such as the Columbia Slough in Portland, Oregon. Both larvae and adults inhabit the same water body: larvae tend to inhabit the benthos, whereas adults inhabit the water column.

Adults are small, with elongated bodies, long legs and long tarsal claws. The elytra are generally dark, and may be patterned with rows of tiny indentations. Larvae have long hardened bodies that may be cylindrical, flattened, or slightly concave.

Size: small to large
Identifying feature(s): antennae long and segments fairly similar in size and shape; hind legs don't have swimming hairs
Habitat: moving water in streams and lake shores; stream riffles; wetlands
Tolerance to pollutants: moderate to tolerant