I saw a banded woollybear caterpillar (Pyrrharctia isabella) this week. Have you heard the folklore about their ability to predict the coming winter’s weather?
Some people say that the wider the rusty band, the milder the winter will be.
There’s a Woolly Worm Festival in Banner Elk, NC every October. They have a caterpillar race, and the winning caterpillar’s segments are read to predict the winter weather.
Scientifically speaking, woollybear caterpillars change color over time. As the caterpillars grow, their black hairs change to brown hairs. Their color suggests how mature the caterpillar is. You could back calculate the life cycle of the moth, eggs and caterpillars for a generation or two to determine how early or late spring came that year. So, technically, the caterpillar you find in the fall can tell you how cold the previous winter was.
You can read more about the woollybear weather folklore on the Old Farmer’s Almanac. NC State Extension has some scientific information on these caterpillars here.