Euproctis chrysorrhoea
In 3 days ~50% in a week ~80%
The brown-tail moth (Euproctis chrysorrhoea) is a moth of the family Erebidae. It is native to Europe, neighboring countries in Asia, and the north coast of Africa. Descriptions of outbreaks, i.e., large population increases of several years duration, have been reported as far back as the 1500s. The life cycle of the moth is atypical, in that it spends approximately nine months (August to April) as larvae (caterpillars), leaving about one month each for pupae, imagos and eggs. Larvae (caterpillars) are covered in hairs. Two red spots on the back, toward the tail, distinguish these species from other similarly hairy moth larvae. The winged adults have white wings and a hairy white body with a tuft of brown hair at the tip of the abdomen. Females lay one egg cluster, usually on the underside of a leaf of a host plant. The species is polyphagous, meaning that it feeds on many different species of trees, including pear, apple, maple and oak.
This species was accidentally introduced to the United States in the 1890s. During the early 20th century it was present from eastern Connecticut northward into New Brunswick, Canada, but a subsequent severe population collapse reduced the territory to parts of coastal Maine and Cape Cod, Massachusetts, by the late 20th century. One theory for the decline appeared to be parasitism by a fly introduced to combat spongy moths. Starting in 2015 there has been a population spike and territory expansion in coastal Maine. In Europe, there are multiple parasitic and predator species, yet there is still a history of population outbreaks.
Hairs from the caterpillars are toxic for humans, causing a poison ivy-like itchy rash of up to sometimes weeks-long duration due to mechanical and chemical irritation. Direct contact with larvae is not necessary, as the hairs are shed and can become windblown. Toxins in the hairs remain potent for up to three years. Outdoor activities such as mowing a lawn or raking leaves in the fall can cause exposure. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Acadia National Park | 🇺🇸 United States | |
| 2 | Wadden Sea National Park | 🇩🇪 Germany | |
| 3 | Vanoise National Park | 🇫🇷 France | |
| 4 | Sierra Nevada National Park | 🇪🇸 Spain | |
| 5 | Pyrénées National Park | 🇫🇷 France | |
| 6 | Sierra de Guadarrama National Park | 🇪🇸 Spain |
Possible
About 20% of wildlife watchers report a Brown-Tail Moth sighting in Acadia National Park on a given day, based on 108 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 11th most-seen of the 405 insects we can rate there. Over three days the chance rises to about 50%, and over a week to about 80%, if each day is a fresh chance.
July
In that month about 40% of wildlife watchers report a Brown-Tail Moth in Acadia National Park on a given day, against under 5% in September to March, the lowest months.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Brown-Tail Moth sightings with a recorded time, and about 7 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 6 parks where we can rate Brown-Tail Moth sightings, Acadia National Park has the highest daily chance: about 20%. Next come Wadden Sea National Park (Germany, about 20%) and Vanoise National Park (France, about 10%).
Same family: Erebidae
The closest relatives of the Brown-Tail Moth that you can see in Acadia National Park (family Erebidae, Underwing, Tiger, Tussock, and Allied Moths) are Hickory Tussock Moth (about 30%), Isabella Tiger Moth (about 20%) and Banded Tussock Moth (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Brown-Tail Moth is recorded against all the insects logged in Acadia National Park (108 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.
