The inchworm is a popular bug that will often drop in if you are hanging out under a tree during the summer. Suspended by nearly invisible thread, the inchworm is a curious little caterpillar that loves to “hang out”. The inchworm is the larval phase of thousands of different species of North American moths.
The inchworm earns its name from the way it moves. When it crawls, it will arch its midsection and inch its way along a surface. Depending on the species, inchworms can have two or three sets of tube-like appendages, called prolegs. Three are located under the head portion of the body and the rest under the tail end. This leaves a gap in the inchworm’s body where there are no legs at all. The larvae inches forward by reaching with its front prolegs and then scooting its abdomen so that its abdominal prolegs meets its front prolegs.
In spring, eggs laid in late summer and fall under leaves by adult moths hatch. The newly hatched inchworms will use silk threads to lower themselves from trees to the ground. The larvae burrow into the dirt or leaf litter and spin cocoons. For several weeks or months, these inchworms pupate, and then they emerge in early spring as moths.
Inchworms feed on trees, shrubs, and crops. They are quite hardy and resistant to insecticides. Biological controls such as predatory wasps and infectious fungi are used instead for population control. This is important, as inchworms can cause significant damage as pests.
Interestingly, female adult inchworm moths can not fly and only have small vestigial (having the property of being a remnant of something once larger or more noticeable). Only the males fly so that they can find females waiting on tree trunks.