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.
I'm not positive of the collection date on this one, so I'm guessing.
This mayfly was collected from unknown in Wisconsin on May 20th, 2004 and added to Troutnut.com by Troutnut on January 25th, 2006.