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Updates from July 5, 2017

Photos by Troutnut from the South Fork Sauk River in Washington

Closeup insects by Troutnut from the South Fork Sauk River in Washington

Male Epeorus (Little Maryatts) Mayfly DunMale Epeorus (Little Maryatts) Mayfly Dun View 12 PicturesI hoped this dun would molt into a spinner for a positive ID, but it didn't. My best guess is Epeorus dulciana, but that's only because that's the smallest western Epeorus species, and this specimen is smaller than any of the others, with a body length of 5.3 mm (although it would be longer as a spinner) and a wing length of 8.5 mm.

It was collected at the same time as a similar-sized female dun.
Collected July 5, 2017 from the South Fork Sauk River in Washington
Added to Troutnut.com by Troutnut on July 6, 2017
Male Rhithrogena virilis Mayfly SpinnerMale Rhithrogena virilis  Mayfly Spinner View 12 PicturesI'm fairly sure this is a specimen of Rhithrogena virilis based on closeup examination of the reproductive anatomy under the microscope (not shown in photos). The other other species of Rhithrogena this large is Rhithrogena flavianula, but the key in Needham's Biology of Mayflies mentions annulation in the abdomen (visible in some images on bugguide.net) more distinct than that on this specimen.

The body and front wing were both about 15.5 mm long, while the cerci (Cercus: The left and right "tails" of an insect are known as the cerci or caudal cerci. The middle tail of a three-tailed insect is not.) were 40 mm long.
Collected July 5, 2017 from the South Fork Sauk River in Washington
Added to Troutnut.com by Troutnut on July 6, 2017
Female Epeorus (Little Maryatts) Mayfly DunFemale Epeorus (Little Maryatts) Mayfly Dun View 5 PicturesI'm guessing this female is of the same species as this male dun, because they came from the same pool at the same time and the size matches, although the males and females would look very different in this case.
Collected July 5, 2017 from the South Fork Sauk River in Washington
Added to Troutnut.com by Troutnut on July 6, 2017

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