Many seasonal cottagers, like us, consider the fall a bitter sweet time of year, sweet because of the glorious fall colours of deciduous trees and bitter because it is when we close up the cottage, watch many birds and insects leave, and see the flowers fade away. Another aspect on the sweet side of the ledger is spotting some interesting caterpillars getting ready for winter.
Many of the caterpillars we see in the fall are fuzzy. One might reasonably think the purpose of their hairy coats is to ward off the colder temperatures. In fact, though, these hairs, also termed setae, often have microscopic barbs, especially those of the caterpillars of the tiger moth family. These barbed hairs provide the caterpillar physical protection from predators as they cause irritation when the barbs get lodged in the predator. Our field guide warns the barbed hairs ‘are allergenic to some people, or prove problematic if dislodged setae come into contact with eyes, mucosal membranes, or other sensitive skin’. Be careful.
Most people are familiar with our first fuzzy caterpillar, the wooly bear with its coat of short orange and black hairs. We most frequently see these caterpillars, which can grow to 5 centimeters, crossing the road near our cottage around the time of the first frost. This caterpillar is the larval stage of the Isabella tiger moth. Some people ascribe these fuzzy little creatures with the ability to forecast the severity of the upcoming winter, suggesting that narrower orange bands indicate a colder winter. The caterpillars overwinter in leaf litter, ready to resume feeding in spring as soon as herbaceous and woody plant vegetation becomes available.
The fuzzy black and white caterpillar of the hickory tussock moth can be found feeding on the leaves of most woody plant species, not just hickory as the common name suggests. The caterpillar can grow to 4.5 centimeters in length by September. They over winter as pupa in a loose cocoon spun in leaf litter. As with other tiger moth caterpillars they weave their setae into their cocoon for protection. Our field guide notes ‘sensitive persons get rashes and associated itching when exposed to the hairs (of this caterpillar), although severe allergic reactions are rare.’
The milkweed tussock moth caterpillar is another fuzzy member of the tiger moth family that we see throughout the summer and into the fall. The yellow-orange, black and white caterpillar can grow to 3.5 centimeters. Unlike its cousin, the hickory tussock moth caterpillar, the milkweed tussock caterpillar feeds exclusively on milkweed and often totally defoliates host plants. The pupa over winter in a cocoon that incorporates their setae.
Our last fuzzy caterpillar is the banded tussock moth caterpillar. This yellow-haired caterpillar can grow to 4.5 centimeters. It gets its common name from the brownish band of hairs along its back. The larva can be found from July into the fall feeding on the leaves of a wide variety of woody plants. As with many other members of the tiger moth family, the pupa over winter in a cocoon that incorporates many of the caterpillar’s protective setae.
Not all fall caterpillars are fuzzy. Here is just one example. The yellow-shouldered slug caterpillar is small and hairless, growing to 1.5 centimeters. This caterpillar feeds on a variety of smooth-leaved woody plants. It was a very exciting autumn day when our young great-nephew spied one at the cottage while he and his parents were visiting. It is a caterpillar that does not quite look like what we would expect of a caterpillar. Instead of paired legs, they have medial suckers on the first seven abdominal segments and so move by gliding rather than crawling. They overwinter in a dense spherical silk cocoon.
These are just some of the many interesting caterpillars we see in the fall which is late in the active season for moth larva. Should you come across any fuzzy ones, we recommend against handling or petting them, even though they look soft and cuddly.
We relied on David L. Wagner’s Caterpillars of Eastern North America for some of the information contained in this article.
