Pyrrharctia isabella

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Isabella tiger moth
Pyrrharctia isabella – Isabella Tiger Moth (14842796231).jpg
Pyrrharctia isabella - Caterpillar - Devonian Fossil Gorge - Iowa City - 2014-10-15 - image 1.jpg
Woollybear caterpillar
Scientific classification e
Kingdom: Animalia
Clade: Euarthropoda
Class: Insecta
Order: Lepidoptera
Superfamily: Noctuoidea
Family: Erebidae
Genus: Pyrrharctia
Species: P. isabella
Binomial name
Pyrrharctia isabella
(JE Smith, 1797)
  • Phalaena isabella Smith, 1797
  • Pyrrharctia californica Packard, 1864

Pyrrharctia isabella, the isabella tiger moth, banded woolly bear or just woollybear, occurs in the United States and southern Canada.[1][2][3] The first European to describe it was James Edward Smith in 1797.


The thirteen-segment larvae are usually covered with brown hair in their mid-regions and black hair in their anterior and posterior areas. In direct sunlight, the brown hair looks bright reddish brown. Adults are generally dull yellowish through orangish and have robust, scaly thorices; small heads; and bright reddish-orange forelegs. Wings have sparse black spotting.

Larval setae do not inject venom and are not urticant; they do not typically cause irritation, injury, inflammation, or swelling.[4] Handling larvae is discouraged, however, because their sharp, spiny hairs may cause dermatitis in some people. When disturbed, larvae defend themselves by playing possum (rolling up into balls and remaining motionless) and quickly crawling away.


This species is a generalist feeder, consuming many plant species, including herbs and trees.[5]

Related species[edit]

Research[6] has shown that the larvae of a related moth, Grammia incorrupta (whose larvae are also called "woollybears"), consume alkaloid-laden leaves that help fight off internal parasitic fly larvae. This phenomenon is said to be "the first clear demonstration of self-medication among insects." Within the same family, the larvae of the garden tiger moth (Arctia caja) are also known as woollybear caterpillars and consume an alkaloid diet similar to Grammia incorrupta.

In culture[edit]


Canadian and U.S. folklore holds that the relative amounts of brown and black hair on a larva indicate the severity of the coming winter. It is believed that if a Pyrrharctia isabella's brown band is wide, winter weather will be mild, and if the brown band is narrow, the winter will be severe. In a variation of this story, the color of stripes predict the winter weather, with darker stripes indicating a harsher winter. In reality, hatchlings from the same clutch of eggs can display considerable variation in their color banding, and a larva's brown band tends to widen with age as it molts.[7] Another version of this belief is that the direction in which a Pyrrharctia isabella crawls indicates the winter weather, with the caterpillar crawling south to escape colder weather. There is no scientific evidence for winter weather prediction by Pyrrharctia isabella. [8]

Woollybear festivals[edit]

Woollybear festivals are held in several locations in the fall.