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. As the name implies, the October Caddis primarily emerges in fall from cool, forested streams, with the life cycle taking one or two years depending on location. The aquatic larvae spin protective cases that incorporate plant materials at first, but change to fine gravel as they mature. According to iNaturalist, “In late spring and early summer the large larvae can be seen meandering over the tops of boulders grazing on diatoms and algae like slow moving cows.”
Kristi had several of these large caddisflies visit her lights at night during the week the photo was taken.
Photo by Kristi DuBois on 9/19/20 in Missoula, MT