Definition
A dobsonfly is a large insect belonging to the genus Corydalus, known for its striking appearance, especially the long mandibles of the male. The aquatic larvae, called hellgrammites, are fierce predators in streams and rivers. Dobsonflies are indicators of good water quality. Their intimidating looks belie their relative harmlessness to humans. They play an essential role in aquatic ecosystems. They're the insect equivalent of a river monster, but much smaller.