THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

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

The family Corydalidae includes dobsonflies (Corydalus) and fishflies (all other genera).

Corydalidae larvae are called hellgrammites; mature larvae can be surprisingly large (up to 90 mm). In the Northwest, they are typically found in rocky bottomed mountain streams. In the eastern US, these large predators can even be found in some urban streams. Corydalid larvae have long flattened bodies and robust toothed jaws. Hard plates cover the top of each throacic segment, and there are flexible gills on each abdominal segment. Unlike the alderflies, corydalid larvae have two short fleshy prolegs at the end of their abdomen; each proleg has 2 sharp hooks at the tip.

The adults are large and distinctive, especially the males, which have long curved mandibles that may be twice as long as their heads, although they do not bite. Adult males of eastern Corydalus have long, tusk-like mandibles. Western Corydalus species have mandibles about half that long, but they are still impressive. It is rare to see the adults because they only live a few days and don't stray far from the stream.