Fauna
Insect

Eastern Dobsonfly

Corydalus cornutus

Also known as Hellgrammite, King Bug, Goober Bug

Eastern dobsonflies are impressive aquatic insects famous for the oversized, sickle-like mandibles of adult males. Their fierce larvae, known as hellgrammites, spend several years underwater in fast-flowing streams as formidable predators before metamorphosing into winged adults. Adults emerge in midsummer, living only a week or two to mate along clean riverbanks and night-lit walls.

NocturnalAquatic LarvaeStriking Mandibles
Eastern Dobsonfly reference1 / 7
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Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & preyMayfly Nymphs, Caddisfly Larvae, Stonefly Nymphs
Predators
  • Freshwater Fish
  • Bats
  • Insectivorous Birds
ThreatsWater pollution, stream siltation, and night light pollution
HabitatsClean rocky streams, rivers, and adjacent riparian forests
Life span2–5 years (larvae); 1–2 weeks (adults)
Classification
  1. OrderMegaloptera
  2. FamilyCorydalidae
  3. GenusCorydalus
  4. SpeciesCorydalus cornutus
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Females and larvae deliver a sharp, painful pinch if grasped; observe safely without handling.
Why it is dangerous
Females and aquatic hellgrammites possess short, powerful jaws capable of delivering a painful pinch that can break skin.
How to recognize a risky encounter
Look for large dark greyish-brown bodies, heavily veined translucent wings, and prominent jaws near swift streams.
What to do
Observe from a safe distance under outdoor lights or along riverbanks; avoid picking them up by hand.
Responsible observation
  • Light Trapping: Search illuminated walls near clean rivers on warm midsummer nights.
  • Handling Caution: Keep fingers well clear of short, sharp female mandibles and aquatic larvae.
  • Stream Health Indicator: Finding larvae under river stones signals clean, oxygenated water.
Related species
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