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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 (Penes: The paired genital structures of most male insects, which vary widely in form and are one of the main characteristics used for species identification.) 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 on July 8th, 2019 and added to on July 18th, 2019.

Recent Discussions of this Spinner

Puzzled on this mayfly, not even confident on family 1 Reply »
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."

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