Sphinx Moth Caterpillar: Caterpillar identification can be very difficult, but we think this is a Snowberry Sphinx moth caterpillar (Sphinx vashti). They inhabit mountain woodlands and prairie stream valleys in western North America. In regard to the name …take a wild guess as to the type of plant the caterpillars feed on. Snowberry. Photo by Kyle Hartse on 8/19/17 near York, MT.