A large alien-looking insect — wingspan up to 7 inches with intimidating mandibles on adult males (which they can't actually bite hard with). The aquatic larvae, called "hellgrammites," are prized as fishing bait.

Also called: Dobson Fly, Hellgrammite (larva)

Native status: Native to eastern North America

§ Quick facts

SizeAdults 8–13 cm wingspan; body 4–6 cm
Weight~1 g
LifespanAdults 7–10 days; aquatic larvae 1–3 years
OrderMegaloptera
FamilyCorydalidae

§ Encyclopedia

The eastern dobsonfly, Corydalus cornutus, is a large insect in the Corydalidae family. The larvae are known as hellgrammites and are among the top invertebrate predators in the streams in which they live, and are used by anglers as bait.

Source: Wikipedia — Corydalus cornutus Licensed under CC BY-SA 4.0

§ Identification

Field marks. Massive moth-like insect with long lacy translucent wings; males with extraordinary curving sickle-shaped mandibles; long thin antennae.

Similar species. Antlions (smaller; clubbed antennae). Some moth species (very different mouthparts).

Voice. Adults: silent. Larvae: hiss when disturbed.

§ Diet & behavior

Diet. Adults: do not feed. Larvae ("hellgrammites"): aquatic predators of insect larvae, small fish, other invertebrates.

Behavior. Among the largest and most impressive insects in eastern North America. Adults emerge in mid-summer and live only days to mate before dying. Males have enormous mandibles up to 4 cm long — used for combat with other males but completely harmless to humans (cannot deliver damaging bite due to leverage). Larvae (hellgrammites) are among the largest aquatic insect larvae in US streams and are highly prized as fishing bait — among the most effective baits for smallmouth bass.

§ Range

Eastern North America

§ Habitat

Clean streams and rivers with rocky bottoms

§ Threats

Stream sedimentation, pollution, dam construction, harvest of hellgrammites.

§ Conservation status

According to the IUCN Red List, the eastern dobsonfly is currently classified as Least Concern.

§ What helps

Support clean cool streams. Maintain stream-side buffer strips. Practice responsible hellgrammite harvest.

Support our work More ways to help

§ Further reading

§ Sources cited

  • BugGuide
  • In-Fisherman Magazine (hellgrammite)
  • University of Florida IFAS Entomology