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 took a few group picture of a bunch of Baetisca laurentina nymphs to show the degree of individual variation in size, color, and shape that can occur within the same species in the same pool of the same river. This variation is one important reason why trout are forgiving of some small degree of variation in our imitations--the naturals themselves vary, too.
This mayfly was collected from unknown in Wisconsin on March 1st, 2004 and added to Troutnut.com by Troutnut on January 25th, 2006.