Spruce moths are often mistaken for caddis and are rarely discussed in depth. There are a few good articles floating around about the hatch but they bugs are often overlooked and underappreciated. The moths are actually a parasite and are hard on fir and spruce trees.
Perfect conditions for their survival have made them prolific in recent history. The recent boom in populations is part of the reason they are not well know. Word just hasn't gotten out.
The moths hatch in the trees during the hot month of August and continue into September. A time when other hatches are stagnant. Montana sees great hatches on the Big Hole, Rock Creek and the Blackfoot River and the moths are prolific throughout the west.
When: August, September
Where: Spruce and Pine Forests. Especially After a Mild Winter.
Indicators: The moths tend to dap the water's surface and dance up and down. They look similar to caddis with tent shaped wings and cream colored body. Fish eat them aggressively, often leaping from the water to catch them. It's a very visual hatch.
Matching the Hatch: A tan elk hair caddis or stimulator is just fine. Dead drift, skate or twitch the fly. Skating is fun and draws the most aggressive strikes.