Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
Litobrancha on Oct 20, 2006October 20th, 2006, 7:59 am EDT
a great thing about cheumatopsyche (which i believe this is) is that the IX segment ventral plates are almost always completely differentiated to the base. hydropsyche medial margins are more indistinct near the base.
also cheumatopsyche almost always lacks F1 in the hind wings, although aberrant specimens are common. the best character is the distance between M and Cu veins in the hind wing, other hydropsychids are parallel and close together, cheumatopsyche diverges a bit.