Blue-winged Olives
Baetis

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.

Stream photos

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Male Rhithrogena hageni (Western Black Quill) Mayfly Spinner Pictures

Although I could not find the preserved specimen to examine under my good new microscope, I'm tentatively calling it one Rhithrogena hageni, based on apparent similarity to this specimen, which I was able to positively ID.

The relative angle of the penes is a bit shallower in this specimen, but I photographed another specimen from the same collecting trip (and I think even the same swarm, although I don't recall for sure) as the other one, and it had the shallower angle seen on this specimen. I'm guessing it's just variation within the species.

This mayfly was collected from the Ruby River in Montana on July 8th, 2019 and added to Troutnut.com by Troutnut on July 18th, 2019.

Discussions of this Spinner

Puzzled on this mayfly, not even confident on family

1 replies

Posted by Troutnut on Jul 23, 2019

Last reply on Jul 23, 2019 by Millcreek

This seems to be some sort of Heptageniid, based on the two tails and five segments on the hind tarsus. Following the key in Merritt & Cummins seems to lead to Rhithrogena, but it doesn't fit a characteristic described in Needham's Biology of Mayflies for that genus: "Tibia of hind leg in both sexes about 1/4 length of femur."