Wandering Caterpillars

 

An Orange-striped Oakworm, Anisota senatoria, caterpillar. The grid marks measure 1/4 inch.
(photo by Dale Hoyt, 8/22/2020)

From late summer through fall you will often see caterpillars crossing sidewalks or streets. One commonly encountered species is the Orange-striped Oakworm (Anisota senatoria). It is black with several yellow or orange longitudinal stripes. (Or is it orange or yellow with black stripes?). Its other prominent feature is a pair of flexible "horns" that arise from the second segment behind the head. Shorter horns are found on the other body segments. 

Orange-striped Oakworm caterpillar nibbling around a gall on a Water Oak leaf.
(photo 8/26/2020; Emily Carr)

 

 

 

 

The caterpillars eat oak leaves, mainly in the red oak group. 

Leaves being stripped by Orange-striped Oakworms.
How many caterpillars can you find?
(photo 8/26/2020; Emily Carr)

 

 

When they have reached the right size they go wandering, looking for a suitable place to burrow into the soil. They excavate a chamber where they will spend the winter in the pupal stage. The moth emerges the following spring.

As caterpillars feed they grow in size and periodically shed their skin, a process called molting. In most butterflies and moths the caterpillar molts five times, the last molt resulting in the pupal stage. With each successive molt the caterpillar not only increases in size, it may change its behavior and/or appearance. The newly hatched oakworms are gregarious -- they feed together on the oak leaves. As they grow and shed their skins they become more solitary, dispersing over their host plant. Their coloration also changes. This species has a single generation per year.