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 haven't seen the imitation of these things stressed, but in August 2003 on one of my favorite rivers the largest brown trout I kept had stomachs full of these things.
This giant water bug was collected from the Namekagon River in Wisconsin on January 13th, 2004 and added to Troutnut.com by Troutnut on January 25th, 2006.