Woolly bear caterpillars and weather
FOR IMMEDIATE RELEASE
October 7, 2013
- Have you noticed all the woolly bear caterpillars lately? Rhonda
Ferree, a University of Illinois Extension horticulture educator, said that
these caterpillars are often seen crossing roads and paths this time of year.
caterpillars are the larval stage of the isabella moth. They are about 2 inches
long, covered with stiff bristles, and are black with a broad band of
reddish-brown bristles around the middle.
caterpillars feed on mostly wild herbaceous plants such as lambsquarter, Ferree
seldom attack desirable plants, once they strip the weeds of foliage they may
move on to flowers and other landscape plants. "Once they move onto desired
plants, they usually are too large to be effectively controlled. In some cases,
handpicking the larvae off the plants may be an option, but in most cases
trying to control these caterpillars this late in the season is not
reasonable," she said
superstition, the amount of black on the woolly bear's bristle coating
forecasts the severity of the coming winter, Ferree said. "It is the relative
proportions of the black and reddish-brown portions of the caterpillar that are
supposed to predict the winter. The longer the black segments on the ends of
the caterpillar, the harsher the coming winter."
associated with forecasting the winter using these insects is that the tiger
moth has similar caterpillars as its larval stage, Ferree explained.
there are nearly hundreds of tiger moth species, and each has a different color
variation. Plus the caterpillars shed their skins, or molt, six times before
reaching adult size and their colors change with each molt," she added.
Donald Lewis, entomologist from Iowa State University, there is some
year-to-year variation in the amount of black hairs on these caterpillars, but
the differences are caused by age and wetness. Older caterpillars have more
black than young ones and caterpillars that fed and grew in an area where the
fall weather was wetter have more black hair than caterpillars from dry areas.
So why do the
woolly bears cross the road?
really knows why, but they cross roads and paths on warm days in late fall,"
Ferree said. "Some people even believe that this can predict the weather. If
they are going south, it is going to be a harsh winter. If they are headed
north, it will be a mild winter. If you are driving east and west, I don't know
what that means," she said.
"If you don't
believe woolly bears can predict the weather, you might instead want to look at
pig spleens, groundhogs, hornets, persimmon seeds, or read what The Old
Farmer's Almanac says. You can watch the weather forecasters using their
high-tech equipment," Ferree said. "Or you can just wait and see what winter
has in store for us. I suggest that you enjoy a beautiful fall day with a nice
walk outside while you wait," she said.
information on this or other horticultural issues, contact an Extension office
by visiting www.extension.illinois.edu. Questions can also be posted on
Ferree's Facebook page at www.facebook.com/ILRiverHort.
Source: Rhonda J. Ferree, Extension Educator, Horticulture, firstname.lastname@example.org