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Science & Nature • Entomology

Dobsonfly

Dobsonflies are large aquatic insects in the subfamily Corydalinae, order Megaloptera, known for the males’ enlarged mandibles and the aquatic larvae called hellgrammites.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

Dobsonflies are large aquatic insects in the subfamily Corydalinae, order Megaloptera, known for the males’ enlarged mandibles and the aquatic larvae called hellgrammites. They are found near moving water and are best known in North America for the eastern dobsonfly, Corydalus cornutus.

Classification

Dobsonflies belong to the order Megaloptera and the family Corydalidae. Sources describe them as a group within the subfamily Corydalinae, with several genera and dozens of species worldwide.

Life cycle and habitat

Dobsonflies spend most of their lives as aquatic larvae in flowing freshwater habitats such as streams and rivers. Adults are short-lived, usually emerging in late spring or summer and living only a few days.

Appearance and behaviour

Adults are large insects with four similarly sized, net-veined wings and long antennae. Males are especially notable for their enlarged jaws, which are used mainly for display and mating rather than defense.

Larvae and ecological role

The larvae, known as hellgrammites, are predatory aquatic insects and are commonly used by anglers as bait. They contribute to stream ecosystems as mid-level predators.

Key facts

  • Dobsonflies are large, net-veined insects in the subfamily Corydalinae.
  • Adults are usually nocturnal and are often attracted to lights.
  • Males have very large mandibles used mainly in courtship, while females have shorter, stronger mandibles that can deliver a painful bite.
  • The aquatic larvae are called hellgrammites and live in streams and rivers.
  • Dobsonflies are associated with clean, moving water and are important predators in aquatic food webs.
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Canadian context

Dobsonflies occur in eastern North America and are reported from Canada, where they are associated with rivers and streams and may be encountered by anglers and naturalists.

Frequently asked questions

What is a dobsonfly?
A dobsonfly is a large aquatic insect in the subfamily Corydalinae, order Megaloptera, with a larval stage called a hellgrammite.
Are dobsonflies dangerous to humans?
They are not considered dangerous, but females can deliver a painful bite. Males have large mandibles that are mainly for display and mating.
Where do dobsonflies live?
They live near moving freshwater, especially rivers and streams, and are found in parts of North and South America, Asia, Australia, and Africa.
What do dobsonfly larvae look like?
Dobsonfly larvae are aquatic, predatory insects called hellgrammites. They live in streams and are known to anglers as bait.
How long do adult dobsonflies live?
Adults usually live only a few days, commonly around 3 to 10 days.
What is the eastern dobsonfly?
The eastern dobsonfly, Corydalus cornutus, is the best-known dobsonfly species in eastern North America.

References

  1. University of Maine Cooperative Extensionhttps://extension.umaine.edu/home-and-garden-ipm/fact-sheets/common-name-listing/dobsonflies/
    Supports: Adult and larval description, behavior, mandibles, habitat, and larval name hellgrammite.
  2. Encyclopaedia Britannicahttps://www.britannica.com/animal/dobsonfly
    Supports: Taxonomic placement, distribution, number of genera, and general characteristics.
  3. WebMDhttps://www.webmd.com/a-to-z-guides/what-to-know-about-dobsonflies
    Supports: Size, lifespan, habitat, distribution, and general biology.
  4. Missouri Department of Conservationhttps://www.mdc.mo.gov/discover-nature/field-guide/eastern-dobsonfly
    Supports: Eastern dobsonfly as the only species in eastern North America.