The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
Earthworms frequently end up in the stream after they make a wrong turn crawling around on a rainy day, and trout relish them. It is interesting that fly fishers frown upon the San Juan Worm, a popular artificial imitaiton, considering that this form of terrestrial hatch-matching is just as rooted in biology as any ant or beetle fisherman's sport.
Since worms fit easily onto a hook, many fishermen skip all the feathers & thread tying and go straight for their favorite all-natural fly pattern: the real, live, wiggling "Garden Hackle."