Inchworms aren’t worms at all, but caterpillars who have legs at both ends of their bodies and none in the middle. This makes them look odd when they move, shifting first one end and then the other, which has the effect of making them arch their bodies as they go. Some people think that they look a lot like a measuring tape and that’s how they got the nickname inchworm. In fact, another name for these small caterpillars is measuring worms.
Inchworms start out in life as eggs, spending the winter attached to the underside of leaves. They hatch early in the spring, and as soon as the tiny inchworms emerge they begin eating. The inchworm has a skin that can’t grow with it, so it needs to shed the old skin when it’s too small. They will molt several times during this stage. When they’ve developed enough, inchworms get a hard shell around them, called pupae, that protect them while they transform into adult geometer moths.
Not all inchworms eat the same foods. This isn’t too surprising since they come from a family that has about 35,000 different species in it worldwide; around 1,400 kinds of geometer moths live in North America. Mostly they eat leaves and fruit. One inchworm doesn’t eat much, but they can cause real problems when they get together in large groups. A hungry bunch of inchworms can seriously damage trees and bushes such as apple, mulberry, blueberry, pine and fir. They’ll also devour the leaves of most garden plants if they get the chance.
Many types of inchworms eat only at night, coming out to feed when fewer predators are around. The darkness also makes it more difficult for predators to find them. Some kinds of inchworms take their chances in the daytime, but they usually have other ways to keep themselves safe.
Some inchworms can spin silk similar to what a spider makes. When danger approaches they can drop quickly from the leaves they are feeding on and hang from the end of a silken strand. The silk is soft at first but gets hard after awhile, and once the danger has passed the inchworms can climb back up to the leaves and go on eating.
An old myth from Kentucky makes reference to the way an inchworm moves, as if he’s taking measurements. Legend has it that if an inchworm crawls on you, he’s measuring you for your coffin. The truth is that he’s probably just looking for something to eat.
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