Corydalus cornutus, known as the Eastern Dobsonfly, is notable for its large size, with males possessing impressive mandibles. Found in North American freshwater habitats, they are indicators of clean water. Its larvae, called hellgrammites, are aquatic and play a crucial role in the food web.

Corydalus cornutus, commonly known as the Eastern Dobsonfly, is native to North America. Its geographical distribution includes the eastern United States and parts of southeastern Canada. The species is typically found in regions stretching from Quebec and Ontario in Canada, down through the eastern and southeastern United States, reaching as far south as Florida and as far west as the Mississippi River region.

Corydalus cornutus thrives in freshwater environments, specifically preferring clean, fast-flowing streams and rivers. These habitats provide the necessary oxygen levels and substrate for its aquatic larvae, known as hellgrammites. The species is often found in areas with rocky or sandy bottoms, which facilitate the larvae's ability to cling and hunt.

The Eastern Dobsonfly occupies a niche as both a predator and prey within its ecosystem. Its larvae are voracious predators of other aquatic insects, contributing to the control of insect populations. In turn, both larvae and adults are important food sources for fish and other wildlife. The species is adapted to life in environments with specific temperature ranges and oxygen levels, making it an important bioindicator for water quality in its native regions.