Royal Alberta Museum: Invertebrate Zoology - Bug Facts

[Caterpillars and Other Immature Insects]

Fact Sheets: Commonly Observed and Asked About Insects and Spiders Found in Alberta

Spotted Tussock Moth (Lophocampa maculata)

Spotted Tussock Moth Caterpillar
Credit: Terry Thormin

Spotted Tussock Moth
Credit: Terry Thormin

INTRODUCTION

The caterpillar of the Spotted Tussock Moth is often called the Yellow Woolly Bear. This is a caterpillar that is often seen crawling around on the ground in the fall, looking for an appropriate place to pupate.

IDENTIFICATION

This distinctive looking caterpillar is quite hairy and banded black, yellow and black. It also has long white hair tufts at each end. In eastern North America, the caterpillar has a row of about four black spots in the central yellow area running right down the middle of the back. These spots seem to be missing in the Alberta population, and perhaps in other western populations. There is also a population in California where the yellow is replaced by orange. The adult moth has yellow-brown front wings with lighter yellowish spots, and pale yellow hind wings. Moths from California have the front wings heavily marbled with darker brown markings. Caterpillars grow to about 4 cm long and the adult moths can have a wingspan of up to 4.5 cm.

DISTRIBUTION

This species is found throughout Alberta, and even into the North West Territories. It is found from the maritime provinces west into British Columbia and south into the mountains of North Carolina and west to southern California.

TIME OF YEAR

In Alberta adults are flying in June and July. The first caterpillars are out by early August and last well into September. This species over-winters as pupae.

HABITAT AND HABITS

Caterpillars feed on a wide variety of trees including poplars, birches, maples, willows and oaks. They are most often seen when they come down out of the trees and go looking for a sheltered place to pupate. Adult moths are nocturnal (active at night) and fly in forested and brushy areas. They are sometimes attracted to lights.

SIMILAR SPECIES

The Woolly Bear caterpillar is the larva of the Isabella Moth (Pyrrharctia isabella). It is rather similar to the caterpillar of the Spotted Tussock Moth, but the yellow is replaced by reddish brown and it lacks the long white hair tufts.

COMMENTS

This common caterpillar is distinctive enough so that once people see it, they are often curious to know what it is. This species is never abundant enough to be a serious pest. Caution should be used if you plan on handling this caterpillar because it has urticating (irritating) hairs to which some people are allergic. The moth is so drab that it is seldom noticed.

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Last update: March 21 2006