Tissue moths overwinter in caves where the temperature stays just above freezing, emerging in early spring. (We suspect that they wait out winter in other protected, temperature-stable locations, too.) A quick search through BugGuide turned up a neat sighting in Montana. In the Columbia Cave, located four miles east of Columbia Falls, “Bryce Maxell and Hans Bodenhamer observed 50+ adult (Triphosa haesitata) moths in the twilight section of the cave.” This section receives a small amount of sunlight since it is not too far from the entrance, and is cool and damp, and its temperature is usually constant. In our area caterpillars feed on leaves of Buckthorn (genus Rhamnus), and if that is not available, Prunus species and occasionally Mahonia (Oregon grape).
Size: Wingspan around 39 mm
Photo by: Kristi DuBois on 3/27/22 in Missoula, MT