the woolly bear caterpillar

Tiser, Gene M TiserG at
Fri Oct 13 12:25:21 EDT 2000

I took some time to look through my library last night for information on
woolly bears.  Note that the moth is called Isabella Tiger Moth, and is
listed as Pyrrharctia isabella (J.E. Sm.) in the Peterson Field Guide.  You
may also find it listed as Isia isabella in other books.

A good reference (should be in the public library) is Donald Stokes' book A
Guide to Observing Insect Lives (1983, Little Brown & Co.).  It has good
information for the general "layperson".  (The entire Stokes Guides series
is fascinating reading - I highly recommend them.  They are not typical
identification guides but rather give fascinating information once you know
what you have).  One of your questions dealt with speed of woolly bears -
the Stokes book lists the speed at 4 feet per minute ( .05 miles/hour )
which is really moving for a caterpillar!

You should also check out the Peterson Field Guide #30 Eastern Moths by
Charles V. Covell, Jr. (1984, Houghton Mifflin Company).   This field guide
mentions that the amount of black and red changes with the instar of the
caterpillar - that is, with every molt, the caterpillar becomes less black
and more red.  (Don't think that another great weather forecast tool may
have just been shot down - see note below in the next book).  They
over-winter as larva and pupate in the spring.  There are typically 2 broods
per year.  It also says the moths are common in the region covered by the
field guide which is North America from 100 degrees longitude east.  I have
no idea of how common they may be in the West......

If the library has a copy, Ninety-nine Gnats, Nits and Nibblers by May R.
Berenbaum (1989, University of Illinois Press) has some interesting
additional human interest tidbits such as Topsell in 1608, in his History of
Serpents, compares the caterpillars to superstitious pilgrims in how they
wander around and eat that which is not none of their own.  He already
refers to them as Bear-worms.  The book also quotes a weather study by C.
Howard Curan of the American Museum of Natural History in New York.  He
compared the caterpillar forecasts to the official weather forecasts from
1947 - 1951 and found the caterpillars to be more accurate!  The forecast is
made based on the amount of red - the more red, the colder/longer the

I had other references but they did not have anything new to add to what is
covered in these three books.

Hope this helps!

> ----------
> From: 	wolfish at[SMTP:wolfish at]
> Reply To: 	wolfish at
> Sent: 	Wednesday, October 11, 2000 8:36 PM
> To: 	leps-l at
> Subject: 	the woolly bear caterpillar
> A friend of mine is a writer, and a chapter or two of a novel she's
> writing hinges on "woolly bear" caterpillars.
> She's had some difficulty finding extensive information on things like
> range, how quickly they move, etc. -- essentially, a day in the life of
> a woolly bear caterpillar. I challenged myself to find the information
> for her.
> Does anyone have a good source of detailed information for the
> layperson, on or offline? Or, better, would anyone be willing to share
> what they know?
> Thank you in advance,
> Wolfish
> Sent via
> Before you buy.

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