Inchworm Moths

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Inchworm Moths (Family Geometridae) are named for the behavior of the caterpillars, which often go by the common name inchworms.

Inchworms, the small caterpillars made famous in songs, cartoons and toys, appear to move inches at a time by curling their body and flattening out.

The movement is a result of their leg structure. While most caterpillar species have 3 sets of legs (true legs) at the front of the body, and five set of legs (prolegs) at the back of the body, inchworms have three pairs of true legs and two pairs of prolegs. The lack of additional prolegs causes the caterpillar to inch along.

Around twelve hundred different Geometridae species can be found in the United States. Many have dull, brown wings complimented by a line pattern. Identifying any particular species can be very difficult.

The subfamily Geometrinae, known as the Emeralds, can be identified as a group by their green wing color.

The top picture shows a yellow-winged species named erastria-decrepitaria.

© 2008 Patricia A. Michaels