Giant Stoneflies

Pronunciation

How to pronounce Pteronarcys: //ˌtɛr.oʊˈnɑːrˌsɪs//

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Summary

Pteronarcys californica, commonly known as the salmonfly, is a species of giant stonefly found primarily in western North America. It undergoes a prolonged nymphal stage in freshwater streams and rivers, emerging as large orange adult insects.

Physical Characteristics

Nymphs can grow to lengths in excess of 5 cm (2 in), with a dark dorsal side and a lighter ventral side. Adults are large with a bright orange abdomen and leg joints, and large wings that are longer than the body.

Identification Tips

Adult salmonflies can be identified by their large size, bright orange coloring on the abdomen and legs, and their two pairs of wings kept flat against the body when at rest.

Habitat

Lives in higher-velocity streams and rivers, on medium to large-sized unconsolidated substrates.

Distribution

Found across western North America, from British Columbia to California; also present in E. Asia with a total of 10 species, mostly in NA, more diverse in the west and Appalachians.

Diet

Nymphs are detritivores, feeding on stream debris; adults do not have a defined diet as they primarily focus on reproduction during emergence.

Life Cycle

Nymphs live for three to four years in the water before emerging, congregating near the shoreline prior to emergence.

Reproduction

Adults carry eggs at the end of the abdomen, resembling a cluster of orange salmon eggs.

Predators

The nymphs are susceptible to predation during their migration to the shoreline before emergence.

Ecosystem Role

As detritivores, they play a key role in breaking down organic matter in aquatic ecosystems.

Economic Impact

Important for fly fishing; many nymph and adult fly patterns are tied to imitate this insect.

Tags

• Giant Stonefly
• Salmonfly
• Pteronarcys californica
• Aquatic Insect
• Fly Fishing