Underwings are masters of disguise, both as caterpillars and adults. Most caterpillars have fringes along their sides that break up their outline and make them more difficult to see when they are at rest on tree bark. Adults conceal themselves with their cryptic forweing patterns as they rest by day. They do have a colorful defense, though, tucked just under their forewings. If they are disturbed into taking flight, the contrasting patterns of their hindwings will flash out, startling predators and hopefully allowing them to get away. Caterpillars feed on leaves of various poplar (Populus deltoides, Populus fremontii, Populus grandidentata, Populus nigra) and willow (Salix). Moths are on the wing from July to September throughout their range of Alberta to Quebec and Maine, south to South Carolina, and west to Colorado and Montana.
Photo by Cec Brown on 7/1/20 in Saint Ignatius, MT.