Malacosoma californica
In 3 days ~20% in a week ~50%
Malacosoma californicum, the western tent caterpillar, is a moth of the family Lasiocampidae. It is a tent caterpillar. The Western Tent Caterpillar is found in southern Canada, the western United States, and parts of northern Mexico. There are currently six recognized subspecies of M. californicum. Western tent caterpillars are gregarious and will spend a large portion of their time with other caterpillars in silken tents constructed during their larval stage.
Western tent caterpillars are univoltine, going through a single generation per year. Adults emerge in the late summer to copulate and lay eggs. Adult moths will preferentially lay their eggs on the sunny side of their host trees. Eggs will lay in diapause over the winter and hatch the following spring. Population sizes of western tent caterpillar can reach outbreak proportions, where populations reach very high numbers and large scale defoliation occurs. Severe outbreaks can cause defoliation of host trees however, damage to trees is minimal and most trees will grow their leaves back quickly.
The mature Western Tent caterpillar pre-pupa is 4-5 centimeters long. The caterpillars are black, grey, or white with... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Glacier National Park | 🇺🇸 United States | |
| 2 | Grand Teton National Park | 🇺🇸 United States | |
| 3 | Joshua Tree National Park | 🇺🇸 United States | |
| 4 | Olympic National Park | 🇺🇸 United States | |
| 5 | Yellowstone National Park | 🇺🇸 United States | |
| 6 | Great Bear Rainforest | 🇨🇦 Canada | |
| 7 | Yosemite National Park | 🇺🇸 United States | |
| 8 | Zion National Park | 🇺🇸 United States | |
| 9 | Rocky Mountain National Park | 🇺🇸 United States | |
| 10 | Jasper National Park | 🇨🇦 Canada | |
| 11 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Western Tent Caterpillar Moth sighting in Yosemite National Park on a given day, based on 26 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 69th most-seen of the 227 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 50%, if each day is a fresh chance.
June
In that month about 20% of wildlife watchers report a Western Tent Caterpillar Moth in Yosemite National Park on a given day, against under 5% in August to April, the lowest months. That is one of Yosemite National Park's driest months, with about 25 mm of rain against 220 mm in January.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Western Tent Caterpillar Moth sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
7th of 11
Of the 11 parks where we can rate Western Tent Caterpillar Moth sightings, Yosemite National Park ranks 7th at about 10%. The best odds are in Glacier National Park (United States, about 30%), Grand Teton National Park (United States, about 30%) and Joshua Tree National Park (United States, about 30%).
Same order: Lepidoptera
The closest relatives of the Western Tent Caterpillar Moth that you can see in Yosemite National Park (order Lepidoptera, Butterflies and Moths) are Limenitis bredowii (about 40%), Pale Swallowtail (about 30%) and California Tortoiseshell (about 30%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Western Tent Caterpillar Moth is recorded against all the insects logged in Yosemite National Park (26 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.
