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The Specimen

Baetis bicaudatus (BWO) Mayfly NymphBaetis bicaudatus (BWO) Mayfly Nymph View 7 PicturesThis specimen was collected along with a female which was quite a bit larger, different in color, but otherwise seemed the same morphologically.
Collected April 12, 2021 from Holder Creek in Washington
Added to Troutnut.com by on April 13, 2021

The Discussion

Post Reply
Brian314February 25th, 2022, 2:22 am
Fenton, MI.

Posts: 51		What are the two red-ish features at the top of the head called ?
TaxonFebruary 25th, 2022, 3:07 am
Site Editor
Royse City, TX

Posts: 1350		Hi Brian-

They are compound eyes, which are curved arrays of microscopic lenses. Each tiny lens captures an individual image, and the insect's brain puts all of the images together to achieve peripheral vision without the insect having to move its eyes or head. This is a mature male nymph, as once mayfly nymphs attain maturity, their wing pads noticeably darken. And, one can tell that it is a male, as a male mayfly has larger eyes, which are positioned on the top of its head, as opposed to a female mayfly, whose eyes would be smaller, and be positioned on the side of its head.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Brian314February 27th, 2022, 3:10 am
Fenton, MI.

Posts: 51		Ah thanks Roger - I thought maybe the dark circle to the side of the head was the eye ... LOL :-)

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