Pest profile

Eastern Dobsonfly

Corydalus cornutus · Megaloptera: Corydalidae[2]

Dobsonflies are among the largest insects in eastern North America; despite their scary look, only the female's short jaws can draw blood.[1]

Male eastern dobsonfly with long, curved tusk-like mandibles, resting on a surface
Male eastern dobsonfly with long, curved tusk-like mandibles, resting on a surface. (c) daksu, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are 4 to 5-1/2 inches long with large wings.[1]
  • Males have long, sickle-shaped mandibles up to 1.6 inches that can't deliver a painful bite.[1]
  • Females have short, powerful mandibles.[1]

Where it lives

It's found through most of eastern North America east of the Continental Divide, near flowing streams where the larvae live.[1]

US map: public records from 36 states since 1990 (GBIF).

Biology and life cycle

Females lay clusters of about 1,000 eggs; eggs hatch in one to two weeks, always at night.[1]

Larvae, called hellgrammites, live under stones in swift, rocky streams and eat soft-bodied insects.[1]

Damage and signs

  • They cause no damage to homes or plants.[1]

Health risk

The female can draw blood with her bite; males can't inflict a painful bite despite their long jaws.[1]

Control

Prevention

No control is needed; they come from nearby streams.[1]

Common questions

Is the giant insect with huge pincers dangerous?
That's likely a male dobsonfly, which can't give a painful bite; females have short jaws that can.[1]
What's a hellgrammite?
The aquatic larva of the dobsonfly, living under stream stones.[1]

Sources

  1. University of Florida IFAS Extension (Featured Creatures), “Eastern Dobsonfly, Corydalus cornutus (EENY-414).” edis.ifas.ufl.edu/publication/IN987 (accessed 2026-10-06)
  2. iNaturalist, “Corydalus cornutus taxon page (order and family).” www.inaturalist.org/taxa/126712 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.