Hellgrammite

Corydalus cornutus — the hellgrammite (the predatory aquatic LARVA of the eastern dobsonfly Corydalus cornutus, with the same scientific name as the adult — already covered in the Wild Files as 'dobsonfly') — is one of the most-cited predatory aquatic insects in eastern North American streams. The species is widespread across all of eastern and central North America from southern Canada south through the eastern US to Mexico. Hellgrammites are 6-9 cm long when fully grown (large hellgrammites approach the size of the human palm), with the species' diagnostic features: a flattened dark-brown elongated body with prominent lateral filaments along each abdominal segment (the gill-like 'tracheal gills' provide oxygen exchange in flowing water); a large head capsule with massive curved SICKLE-LIKE JAWS (the mandibles can extend forward dramatically and are powerful enough to seize and crush large aquatic prey); and short walking legs underneath the body. Hellgrammites are voracious AQUATIC PREDATORS in fast-moving streams and rivers — they hide under streamside stones during the day and ambush passing aquatic prey (smaller insect larvae, small fish, tadpoles, crayfish, other arthropods). Hellgrammites are one of the most ecologically important aquatic predators in eastern NA stream ecosystems and serve as 'apex' invertebrate predators in many streams. The species is one of the most-prized LIVE BAITS in eastern NA freshwater fishing. Fishermen collect hellgrammites under streamside stones (typically by overturning rocks at the stream bottom — the larvae are visible underneath in their resting positions during daylight hours) and use them as live bait for bass (especially smallmouth bass), trout, walleye, and other gamefish. Bass and trout cannot resist hellgrammites — the prey item's size, movement, and natural occurrence in streams makes it irresistible to large predatory fish. The species is featured in essentially every NA freshwater fishing guide and is one of the most-discussed live baits in modern freshwater angling. Hellgrammites can deliver a PAINFUL BITE to humans handling them carelessly — the powerful jaws can pierce human skin and the bite is reported as being similar to a small wasp sting. Anglers who collect hellgrammites typically handle them with care or use forceps. After 1-3 years of aquatic development as hellgrammites, the larvae crawl out of the stream onto streamside soil and pupate underground for several weeks before emerging as ADULT DOBSONFLIES (already in the Wild Files) — large flying insects with up to 15 cm wingspan and dramatic male tusks that look terrifying but are non-functional in feeding (males use them in display to females and rival males). The species is a flagship subject in NA stream ecology and freshwater fishing.