JUNE
2006

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

6-22-06

Download the audio of On Six Legs: MP3, WMV.

By Any Other Name, It's a Caterpillar Just the Same


Caterpillars, according to the Oxford Dictionary, are small creatures, like worms, with legs that develop into butterflies or moths. The Latin roots catari and pilos, which are the basis for the name caterpillar, mean cat and hairy. One must assume that ancient people saw such a striking similarity between a creeping feline and some of this group of immature insects that they referred to them as cata pilos. Hence, the modern name caterpillar.

The insect order Lepidoptera, which includes butterflies and moths, contains a lot of species. Some 11,000 can be found in North America. This means that there are many different types of caterpillars. But all caterpillars have some things in common. They have a well-developed head with chewing mouthparts. The head does not have eyes but usually has 6 eyespots called ocelli and a pair of short antennae.

Caterpillars have six legs associated with the thoracic segments of the body. However, caterpillars also possess additional leg-like appendages called prolegs. Most times there are five sets of prolegs, although some caterpillars have less. The prolegs are fleshier than the true legs and have tiny hooks at the end.

Prolegs function to attach caterpillars to surfaces, primarily to plants. Most caterpillars feed on plants, and prolegs allow them to keep a firm grip on their food. All living things need food, but caterpillars seem to exist for the purpose of eating. Caterpillars are feeding machines that grow while accumulating and storing enough nutrients to support the change into the adult stage. Eric Carle captured the essence of a caterpillar nicely in his children's book, "The Hungry Caterpillar."

Caterpillars also have the ability to produce silk. The silk comes from modified salivary glands located in the caterpillar head. The silk is used to make a cocoon for pupation or to produce a shelter for the caterpillars as they feed.

Full-grown caterpillars can range in size from a few millimeters to over six inches long. Some have a ferocious look, a few produce an offensive odor and some have stinging hairs. But, for the most part, caterpillars are harmless to handle, even though they will hang on with those prolegs and, on occasion, will pinch you with their mouthparts. Just testing, no doubt, to find out if you are a food source!

In addition to the general term caterpillar, other names are sometimes used for some groups of these immature insect larvae. For instance, caterpillars of one group of moths are called measuring worms. These caterpillars lack prolegs in the middle portion of their body and move by forming a loop with their body. Hence, they are also called loopers. In recognition of this type of movement, the scientific family name is Geometridae.

Caterpillars of sphinx or hawk moths are known as hornworms. It is the presence of an obvious horn on the rear end of these caterpillars that is the basis for the name. Even though some people think the caterpillar can sting with the horn, it cannot. The horn is a decoration to make the insect look dangerous. The tomato hornworm can sometimes be found chowing down on our tomato plants.

Silkworms are the caterpillars of the moth named Bombyx mori. This is the insect that is used to commercially produce silk. After feeding on mulberry leaves, the caterpillar spins the silken cocoon as a pupation chamber, which humans have learned to unwind to produce silken thread.

Another group of caterpillars are called wooly bears. These caterpillars get their name because they are very fuzzy. One wooly bear that is black with a brown strip in the middle is purported to predict the severity of the winter.

Other caterpillars are called armyworms because they march in great masses from feeding site to feeding site. Some are called cutworms because they cut plants during feeding. Others, like the European corn borer, are called borers because they feed by boring inside of plants.

Hornworms, silkworms, measuring worms, cutworms and wooly bears are all caterpillars. You can be sure that, because these are names for caterpillars, one of the things they have in common is that they are eating machines.

 

 

Writer: Tom Turpin
Editor: Olivia Maddox