Species Insects & ArthropodsGiant Salmonfly

Giant Salmonfly

Pteronarcys californica

CommonInsect & Arthropod
Illustration of Giant Salmonfly (Pteronarcys californica)

The Giant Salmonfly is one of the largest stoneflies in North America, with orange-red coloration on the abdomen and head that makes masses of emerging adults look like orange blizzards along western rivers. The annual hatch on rivers like the Madison is one of the most celebrated events in fly-fishing, with trout feeding intensively on the large emerging insects. Nymphs require 2–4 years in clean, cold streams.

Habitat
Clean, cold, fast-flowing mountain rivers and streams
Diet
Nymphs: algae, plant detritus, and organic matter. Adults: do not feed significantly
How common
Common

Best time to see a Giant Salmonfly

The best time to see a Giant Salmonfly is April–June, when about 62% of U.S. sightings happen, based on 352 research-grade iNaturalist observations.

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Recent Giant Salmonfly sightings near you

Live, research-grade observations from iNaturalist. Allow location to center the map on you.

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