When I was a kid we used to collect periwinkles in the Cedar River and watch them crawl around in the bottom of a yogurt container. These critters fascinated me with their carefully crafted stone cases and little heads and legs that would cautiously emerge from their mobile homes and lumber around. As I learned to fly fish and began to study entomology, I found out these were Dicosmoecus, also known as the October caddis larva. These aquatic insects generally emerge during the late summer and fall months throughout the west and provide one of the last big bug morsels trout are going to taste before the menu switches to tiny blue winged olives and midges into the winter.
I love fishing big foamy dry flies whenever the opportunity presents itself, from golden stones to hoppers and the October Caddis hatch is one of my favorites. It's partly an attraction to the savage way in which trout tend to pursue these active critters as they wake and twitch on the surface. The other appeal is that I can see a #6 October Caddis from a distance with ease, something my aging eyes struggle with when it comes to the little #20 baetis and other miniscule flies.
The Chubby Chernobyl absolutely crushes big trout throughout western rivers and beyond. The standard orange one works well enough, but I've found that tweaking the body color to more closely match the natural catches more fish, as does switching the wing color to a more muted dun grey instead of the traditional white. Fish this fly actively, twitching the rod tip on a dead drift and even let it swing in the current at the end of the presentation. These big caddis often buzz about the surface like a motor boat and trout are very accustomed to seeing them struggle violently when they end up in the water. Add a few to your box and give them a shot over the next couple of months.