Identifying Tussock Moth caterpillars to genus is not too hard. Getting them to the exact species can be a bit more challenging. We believe this is the Variable Tussock Moth Caterpillar (Dasychira vagans). This species is widely distributed in forests throughout North America. Here in MT, they seem to be a bit more rare, likely being found in mixed hardwood-conifer forests at higher elevations. They are foodplant generalists, feeding primarily on hardwoods such as Aceraceae, Betulaceae, Fagaceae, Salicaceae, and Rosaceae, but particularly favors oaks (Quercus spp.). To see what the adult moths look like, check out the link here

Size: Adult Males – forewing length 14 – 18 mm / Females – forewing length 22 – 24 mm 

Photo by: Megan Phillips on 7/15/22 near Lewistown, MT