Hello:

Thank you for your message with attached image and for contacting Iowa State University. The caterpillar is the larva of one of the underwing moths.  The underwing moths are medium-sized, drab-colored moths except for the brightly colored, striped hind wings for which they are named.

Your specimen appears to be the species with the unusual name, "the Bride."  Compare to the image at  
https://bugguide.net/node/view/521615/bgimage

The common name comes from the scientific name,Catocala neogama.  Neogamma is Greek for "newlywed."  https://bugguide.net/node/view/30844

https://www.butterfliesandmoths.org/species/Catocala-neogama

The caterpillars feed on the leaves from black walnut, hickory, and oak tress. These caterpillars are not a pest of trees. Their feeding does not cause significant harm to trees. Fully-grown caterpillars wander away from the host plant in search of a place to pupate and transform to the adult moth, Your caterpillar has finished eating and won't cause any further defoliation of the nearby tree where it spent it's life up to this point.

These caterpillars are know n for their high activity level when disturbed.  They can wiggle violently when they are not "running."

Thanks.

Donald Lewis