Tom Turpin
Professor of
Purdue University


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Caterpillar Encounters Escalate During Fall Months

Most people enjoy encounters with butterflies. These living flowers add dabs of color and whimsy to our gardens and roadsides. But we aren't as fond of moths and caterpillars. Moths are drab and reclusive, and caterpillars have been described as nothing more than creeping plant chompers.

When the calendar rolls around to August and September, caterpillars are likely to creep from their summer hiding places and into our lives. Yes, the fall season brings with it numerous encounters of the caterpillar kind.

Immature butterflies and moths are both called caterpillars. The word caterpillar is based on the Latin catta pilosa, which means hairy cat. It seems likely that the term caterpillar was first used for immatures of moths. That is because moth caterpillars are often hairy--covered with hair and spines.

Scientists note that the amount of hair that a caterpillar possesses might be a hint as to whether it is to become a butterfly or moth. Butterfly caterpillars are hairless, while moth caterpillars tend to be hairy. But several species of moths have caterpillars that are smooth-skinned and without hair. So, when you discover a hairy caterpillar, you can be certain that it will turn out to be a moth. A smooth caterpillar will probably become a butterfly, but not always!

Some of the most recognizable moths spend their immature days crawling around as hairless caterpillars. These include the flower-feeding moths known as hummingbird moths. Their caterpillars are called hornworms and are very smooth-skinned, as anyone who has picked one off a tomato plant knows.

It is the hairy caterpillars that really attract our attention. Some of the most noticeable are immatures of what are called the giant silkworm moths. These are the cecropia, promethea and polyphemus moths. Their larvae are not fuzzy, but they are large caterpillars. Each is nearly 3 inches in length. Their size, combined with an assortment of spines and knobs, results in rather impressive-looking caterpillars.

There are three species of the giant silkworm moths common in the eastern United States. These caterpillars feed on the leaves of hardwood trees. One is the cecropia. Its larvae are green-colored with studded protrusions on each segment. The polyphemus caterpillar is also green-colored but lacks the studded protrusions. It does have tufts of spines emerging from red spots. The promethea caterpillar is bluish-green in color and has two short, red horns near the head.

A striking large, green moth with long tails, the luna moth, has a caterpillar that resembles those of the giant silkworm moths. It also is green in color with red-marked tuffs of bristles on each segment.

Probably the most fearsome looking of the giant caterpillars is that of the regal moth. This caterpillar has large, red, curved horns near the head. It is appropriately called the hickory-horned devil!

The caterpillars of the giant moths are harmless. They look fearsome and, sometimes, act as if they are trying to bite. There are hairy caterpillars that really are dangerous because they have stinging spines or hairs. One such is the Io moth. This green caterpillar has a red-and-white stripe along the side.

Another stinging caterpillar is called the saddleback. These caterpillars are slug-shaped and green in color with a brown-and-white saddle-shaped mark across the middle. The easily recognized color pattern is called warning coloration, because the caterpillar spines will produce skin irritation when handled.

Other fuzzy caterpillars that are noticeable in the fall have been touted as winter-weather predictors. These so-called wooly bears are said to predict the severity of the winter, based on thickness of the coat, width of the black band or direction of travel. The only thing that the wooly bear caterpillar can predict with accuracy is that winter is on the way.

When fall arrives, all caterpillars stop feeding and crawl around looking for a place to hibernate. The process is called wandering. So, when you encounter a wandering caterpillar, the best advice is look but don't touch. After all, some of those fuzzy caterpillars are armed with stinging hairs.



Writer: Tom Turpin
Editor: Olivia Maddox