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.
Troutnut on Apr 6, 2010April 6th, 2010, 1:08 pm EDT
Going to genus level for the Baetidae can be really tricky, and species level is even harder. The scientific keys don't provide any way to identify the female duns. It may be that someone very familiar with the family can recognize it by sight, but if I were to try I would have to fall back on the standard angler's method of identifying Baetids: pull a name out of a hat. "Let's see here... it's (rummage rummage rummage)... it's Baetis vagans" (That's no longer a valid species, but it is the name that seems to get pulled out of the hat most often.)
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist