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.
Here's a puzzling nymph. It seemed to have double-banded tibiae, although the second band wasn't very pronounced. It has quite prominent tubercles that definitely aren't black.
This mayfly was collected from unknown in Wisconsin on March 10th, 2004 and added to Troutnut.com by Troutnut on January 19th, 2006.