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.
Entoman on Apr 8, 2013April 8th, 2013, 3:27 pm EDT
The occipital ridge shows this specimen to be in the subfamily Perlinae. The distinctive head markings connote a form of Agnetina capitata I've seen in photos of Midwestern specimens. I'm not positive on this one as I can't vouch for the accuracy of the photos compared with it, but I hated to see this guy languish on the family page when it's clearly Perlinae.