The Great Spangled Fritillary (Speyeria cybele) ranges over much of North America and is a common butterfly in the Ozarks. But I had never seen its caterpillar before today. One was making his way across my driveway and since I almost always have a camera at hand, there are photos. 
These caterpillars feed at night, specializing on Viola species and hide under leaves and debris during the day. After mating in early summer, the female lays her eggs singly on a host plant in late summer/early fall and after hatching, the caterpillars overwinter before beginning to feed. Its pupa is camouflaged to look like a dead leaf. The adults feed on the nectar from a variety of flowers.