Pteronarcys californica
In 3 days ~20% in a week ~40%
Pteronarcys californica is a species of insect in the family Pteronarcyidae, the giant stoneflies and salmonflies. It is known commonly as a salmonfly. Salmonflies are an important aquatic insect for fly anglers and many nymph and adult fly patterns are tied to imitate this insect.
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... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Yellowstone National Park | 🇺🇸 United States |
More parks will be added in future updates.
No species of the same family or order lives in Yellowstone National Park, so these are its closest relatives here: other insects.
With luck
About 10% of wildlife watchers report a California Giant Stonefly sighting in Yellowstone National Park on a given day, based on 12 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 72nd most-seen of the 160 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 40%, if each day is a fresh chance.
June and July
In those months about 10% of wildlife watchers report a California Giant Stonefly in Yellowstone National Park on a given day, against under 5% in August to May, the lowest months.
Between 9 am and noon
Across all the parks we cover, that three-hour window holds the most California Giant Stonefly sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Only Yellowstone National Park, in our data
Yellowstone National Park is the only park on Wallace's Line with enough records to rate California Giant Stonefly sightings: about 10% of wildlife watchers there report one on a given day.
GBIF citizen-science records
It is estimated from how often the California Giant Stonefly is recorded against all the insects logged in Yellowstone National Park (12 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
