Wooly Bears

We see them every fall.  Fuzzy, black and orange striped caterpillars inching along the ground, up walls and trees, and across driveways.

Most of us have heard that you can predict a harsh or mild winter by the size of the colorful markings, yet few of us ever consider where this caterpillar comes from or where it is going.

Like many insects, this one starts its life as one of a clutch of miniscule eggs stuck to the bottom of a leaf.

Upon hatching, it feeds on herbaceous plants, and forbs (wild flowers). It is commonly found in milkweed.

The tiny caterpillars share little resemblance to the Woolly Bear with their scrawny bodies and widely spaced tufts of hair. But given just a few weeks they become much more recognizable.

When the caterpillar approaches maturity, it will find a protected place to pupate.  The pupal cases look very much like grayish-brown, oval shaped knots of wool and can often be found adhered to the undersides of eaves.

By Steve Jurvetson from Menlo Park, USA (A Moth is Born) [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

After completing its metamorphosis it will emerge as an adult Tiger moth.

The Tiger moth has a unique characteristic that has only recently been discovered.  In the presence of predatory flies that lay their eggs in the developing caterpillar they will feed on leaves with higher alkaloid content making themselves less vulnerable to the fly.

For the most part, this moth is more amusing than troublesome. Occasionally, they will attack commercial crops like sunflowers.

So the next time you ask a Woolly Bear how cold it’s going to be, you will know what it will look like when it grows up.

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