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.
Were you planning to include pictures?
Yeah, they are. About 10 to 15% are the dark ones.
Why are some dark and some light. Are they different sub-species?
Nice pics!
Most of the hatches you've fished out West were NOT E. D. infrequens (though they were PMD's),
By the time the little guys come around, the fish are quite picky.
By the time the little guys come around, the fish are quite picky. Cripples, nymphs, and emergers become the order of the day - and it's becoming increasingly more difficult to fool fish on hard fished waters after the first month.