At first glance, caddisflies look much like their closest living relatives — the moths and butterflies. How to tell the two groups (orders) apart? Zoom in on their wings and mouthparts. Moth wings have a shingled covering of scales, rather than hairy-like setae, and most moths have straw-like mouthparts (proboscides), rather than mandibles.
Part of the larger family of Northern Caddisflies, winter caddisflies are sometimes called snow sedges. The aquatic larvae develop in freshwater in a tube-like case of stones and bits of plants, feeding on detritus or algae, before emerging in the fall.
According to Marry F. Wilson, a retired professor of ecology and author of “On The Trails”( a weekly column that appears in the Juneau Empire every Wednesday), “ both males and females have been found at times of very cold temperatures—as low as minus twenty or thirty degrees Centigrade, having emerged from their freshwater larval stage in the fall. When they emerge, they are adult in form but sexually immature. They mature gradually during winter, using up stored body fat in the process and females developing their eggs. They mate and lay eggs (in open fresh water) in early spring, and then apparently die, after a life span of roughly six months.” See the full article here. Photo by Gage Poore on 1/1/21 on the Lee Creek Interpretive Trail near Lolo, MT.