mayfly on my automobile

Found this pretty big feller on the hood of my car this evening. This is by far the biggest mayfly I have ever seen around these parts. Its a camera picture, so excuse the quality.

I put a dime next to it for a size reference. Its quite a pretty bug

Any guesses what it is? I would guess march brown, but I don't have my hatch guide to western streams book handy as it was stolen by my 2 year old daughter so she could flip through pages saying "BUGS! FLIES!"



Staff member

I believe this male imago to be of genus Rhithrogena. And based on its body length, which I estimate to be 13.425 mm based on it being 3/4 the diameter of a dime (17.9 mm), it is likely to be R. flavianula. So, your guess of (Western) March Brown is spot on.