Winter Weather Outlook From The Woolly Bear Caterpillar
October 25 2022
In the Northeast US there are two creatures in nature that are most popular in foretelling a long range winter weather outlook. Before the season Woolly Bear Caterpillar spotting is a very common pastime. Mid winter the spotlight goes to Punxsutawney Phil, that groundhog in western Pennsylvania.
Since we are in the heart of Fall, let’s focus on the Woolly Bear, also known as Fuzzy Bear or Woolly Worm. It has even been called a Hedgehog Caterpillar because it curls up into a ball for protection and plays dead. This is the early phase in the life cycle of what will become a tiger moth.
Woolly Bear Folklore
The wider the brown (middle) band on a woolly bear caterpillar, the milder the winter?
Two ways to look at them:
- The Orange Band: This stripe in the middle will be wider when the upcoming winter is expected to be mild.
- The Black Bands: The thicker or more dominant these are means a longer and harsher winter ahead. Translation: More cold and snow!
What determines the colors?
The bands are determined by how long the caterpillar has been feeding, age, and species.
A better growing season means it ate more. The result is a lager caterpillar and smaller orange band. So the color actually shows the prior growing season. However, there is some winter weather folklore that would correlate the summer season and cross to winter snow, so there still could be a connection.
The caterpillar can molt or shed its skin up to 6 times, each one getting a little more orange.
There are 260 known species of tiger moths.
But what about an all black caterpillar?
Does that mean we are in for a Polar Vortex followed by Ice Age conditions? Faith in the Flakes! I’ve even seen a few all light brown or blonde. Would that mean a snow free winter?
Video: All Black/No Orange Stripe
FITF Fans: Does this mean a very harsh winter ahead?
I posted this video on Monday as one crossed my driveway….
Comparing Caterpillars: DIFFERENT SPECIES
Lighter color: Yellow Bear (Spilosoma virginica). These turn into a Virginian Tiger Moth
The striped caterpillars or classic Woolly Bears (Pyrrharctia isabella) turn into a Tiger Moth
The all black caterpillars (Hypercompe scribonia) turn into a Giant Leopard Moth
If we ‘follow the science’, the relative width of the black band varies with age, and has nothing whatsoever to do with weather (Wagner 2005).
But wait! Mike Peters, an entomologist at the University of Massachusetts, says there could, in fact, be a link between winter severity and the brown band of a woolly bear caterpillar. The width of the brown band does say something about a heavy winter or an early spring. That is winter and spring, the previous year, when the caterpillar started crawling.
Note: These caterpillars can survive through the winter, producing their own antifreeze.
If we want to stick with the folklore, then here is a more elaborate break down of color patterns and winter.
History Of Celebrations
From the National Weather Service Archives:
The popularity of the woolly bear caterpillar has resulted in several festivals honoring them. Since 1973, the residents of Vermilion, Ohio have held an annual “Woolly Bear Festival“. The festival is the brainchild of legendary Cleveland TV personality Dick Goddard, longtime weatherman at WJW-TV. It is claimed to be the largest one-day festival in Ohio. Festivities include a parade, woolly bear races and an “official” analysis of the woolly bears and forecast for the coming winter.
Also, every 3rd weekend in October the annual Woolly Worm Festival is held in Banner Elk, NC. They begin their worm races around 10:20 AM, or as soon as the first heat, on Saturday morning. Races continue all day until the grand final about 4 PM when the champion worm and trainer is crowned (and paid!). At that time, the official winter forecast will be declared. Sunday worm races are for fun and small prizes and will continue throughout the day as long as there are race participants.
Other festivals are held in Beattyville, KY (began in 1987); Lewisburg, PA (began in 1997); Oil City; PA (began in 2008); and Lion’s Head, Ontario (began in 2011).
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