**Female Siphlonurus alternatus (Gray Drake) Mayfly Spinner Pictures**

Mayflies

Caddisflies

Stoneflies

Classification

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Siphlonuridae (Gray Drakes)

» Genus Siphlonurus (Gray Drakes)

» Species alternatus (Gray Drake)

I'm tentatively classifying this one as Siphlonurus alternatus, because it seems to fit that species best in the old keys in Needham's Biology of Mayflies, but I'm hesitant because I can't find documentation that southwest Montana or the surrounding area is within the species' range, although they are widely distributed throughout eastern North American and western Canada.

This mayfly was collected from the Gallatin River on July 2nd, 2019 and added to Troutnut.com on July 18th, 2019.