|Isabella tiger moth|
(JE Smith, 1797)
Pyrrharctia isabella, the isabella tiger moth, banded woolly bear or just woollybear or woolly worm, occurs in the United States and southern Canada. 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. 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.
Research 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.
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. 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. 
Woollybear festivals are held in several locations in the fall.
- Vermilion, Ohio, in October, begun in 1973, the Woollybear Festival features woollybear costume contests for children and pets and the Woolybear 500 caterpillar races.
- Banner Elk, North Carolina, begun in 1977, features crafts, food, and races. The winning woollybear predicts the winter weather for the following winter.
- Beattyville, Kentucky, begun 1987, called the "Woolly Worm Festival", features food, vendors, live music, and a "Woolly Worm Race" in which people race the woollybear caterpillar up vertical strings.
- Lewisburg, Pennsylvania, in early fall, begun in 1997, featuring crafts for kids, food, games, a pet parade, and a "Weather Prognostication Ceremony".
- Oil City, Pennsylvania, Woolley Bear Jamboree, begun in 2008, features "Oil Valley Vick" to predict the winter weather. Though some may have hoped[by whom?] he can someday draw a crowd similar to Punxsutawney Phil, Oil Valley Vick made his first and only prognostication in 2008.
- Lion's Head, Ontario, it has been held for two years now to rival Wiarton Willie.
- Little Valley, New York has held a "Woolley Bear Weekend" [sic] since 2012.
- "Entomology Collection > Pyrrharctia isabella". www.entomology.ualberta.ca. Retrieved 28 September 2018.
- "Entomology Collection > Specimen Plot". entomology.museums.ualberta.ca. Retrieved 28 September 2018.
- "Isabella Tiger Moth (Pyrrharctia isabella)". iNaturalist.org. Retrieved 28 September 2018.
- "Woolly Worm Festival". Woolly Worm Festival. Retrieved 2018-10-09.
- Mullen, Gary Richard; Lance A. Durden (2002). Medical and Veterinary Entomology. Academic Press. ISBN 0-12-510451-0.
- "Entomology Collection > Pyrrharctia isabella". E.H. Strickland Entomological Museum, University of Alberta. Retrieved 2008-11-21.
- ""Woolly Bear Caterpillars Self-Medicate -- A Bug First" - National Geographic". Retrieved 2009-03-14.
- Predicting Winter Weather: Woolly Bear Caterpillars, The Old Farmer's Almanac, 1999.
- Service, US Department of Commerce, NOAA, National Weather. "Woolly Bear Caterpillar - Winter Predictor Or Not?". www.weather.gov. Retrieved 28 September 2018.
- "Woollybear Festival »". vermilionchamber.net. Retrieved 28 September 2018.
- Old Farmer's Almanac, 1999.
- Robertson, Dan. "Oil Valley Vick & the NWPA Wooly Bear Society". Mystic Outer Rim Society. Archived from the original on 3 March 2016. Retrieved 29 March 2012.
- County, Cattaraugus (24 July 2015). "Wooly Bear Weekend with Local Manufacturers and Artisans". Cattaraugus County. Retrieved 28 September 2018.
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