California Giant Stonefly

Pteronarcys californica nymphs, or larvae, can grow to lengths in excess of 5 centimetres (2 in). The nymphs' dorsal side (back) is dark in colour, although their ventral side (belly) is lighter. The colouring can vary, and subtle patterns are occasionally found on the abdomen. They are detritivores, eating stream debris partially broken down by other organisms. They are "shredders" as a functional feeding group, breaking down large bits of detritus down into smaller ones while feeding. The adults are also large, and the abdomen, leg joints, and several thorax joints are a bright orange colour. Two pairs of large wings, kept flat against the body when at rest, are longer than the body. The adult carries its eggs at the end of the abdomen and look like a cluster of orange salmon eggs.

Pteronarcys californica is found across western North America, from British Columbia to California. They live in higher-velocity streams and rivers, on medium to large-sized unconsolidated substrates.