Montana Field Guide

The forewing of the Ranchman's Tiger Moth (Platyprepia virginalis) is black with many large and round yellow spots. The hindwing is variable, either orange with black bands or mostly black with orange spots. The thorax is black with dorsal-anterior patches of yellow. The wingspan is about 62 mm (USGS 2006).

Shropshire and Tallamy (2025) provide a list, with synonymies, of 13,055 described native, exotic, and occasional straying Lepidoptera species of North America, north of Mexico; known but undescribed taxa, taxa with unresolved taxonomy, and excluded species are also included. The main manuscript includes links to supplementary materials, including a reference list for Lepidoptera of North America north of Mexico, and a filterable spreadsheet with information on taxonomy, synonymy, size ranges of species, distribution by state, province, and country with references, and host-plant Family and Genus associations with references.

Ranchman's Tiger Moths fly during the day in early summer (USGS 2006).

St. Lawrence Tiger Moth (Platarctia parthenos) is similar to the Ranchman's Tiger Moth, but it's forewing is brown with small yellow spots and its thorax is red-brown. The St. Lawrence Tiger Moth is uncommon and restricted to the northern Rocky Mountain region including the Blue Mountains (USGS 2006).

The larvae are generalist feeders on foliage of herbaceous plants (USGS 2006).