Drasteria petricola
In 3 days ~10% in a week ~30%
Drasteria petricola, the little arches, is a moth of the family Erebidae. The species was first described by Francis Walker in 1858. It is found in western North America from Yukon and the Northwest Territories south to New Mexico in the Rocky Mountains, east to Manitoba.
The wingspan is about 34 mm. Adults are on wing from May to July. The larvae feed on Hedysarum species. Adults feed on the nectar of flowers, including mint in Utah. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Banff National Park | 🇨🇦 Canada | |
| 2 | Olympic National Park | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Little Arches sighting in Olympic National Park on a given day, based on 9 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 150th most-seen of the 207 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
June and July
In those months about 10% of wildlife watchers report a Little Arches in Olympic National Park on a given day, against under 5% in August to May, the lowest months. Those are among Olympic National Park's driest months, with about 60 mm of rain a month against 370 mm in November.
Between 2 and 5 pm
Across all the parks we cover, that three-hour window holds the most Little Arches sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
2nd of 2
Of the 2 parks where we can rate Little Arches sightings, Olympic National Park ranks 2nd at under 5%. The best odds are in Banff National Park (Canada, about 10%).
Same family: Erebidae
The closest relatives of the Little Arches that you can see in Olympic National Park (family Erebidae, Underwing, Tiger, Tussock, and Allied Moths) are Spotted Tussock Moth (about 10%), Silver-Spotted Tiger Moth (about 10%) and Virginian Tiger Moth (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Little Arches is recorded against all the insects logged in Olympic National Park (9 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.
