Moved from Isonychia.

It has a rather elongated head... well... more so then most adult mayflies. It's rather compact...

Moved from Frass.

I think this shot shows the variation in color and markings of this genus very well, and would be a good addition to the Isonychia genus page. Please don't take the comments below to mean that the ID is doubtful at the genus level--it is not. The vast majority of Isonychia females (and many males as well) are just very difficult to take to species through photos.

Moved from ID Request.

"The white spot doesn't set off any bells in my mind. Do you have a copy of Kondratieff & Voshell? They might mention it."

I think Luke overestimates my resources. The publication in which I found mention of this light area between the eyes of some female Palearctic Isonychia was available online, but the K&V publication on North and Central American Isonychia is not and is apparently out of print as well.

Oh well, I tried. Unless someone else has access to a copy of the K&V work and would like to check, the question of whether this is a reliable trait of some species or just a variable trait (like the white "racing stripe" on the backs of some Isonychia bicolor nymphs) will remain open in my mind.

By the way, the more I look at your striking specimen, the more it reminds me of a white-faced Hereford cow. (And that's a sure sign that I have been staring at it for way too long!) :)

I have good news and bad news.

The good news (at least for me) is that the unusual view in your photo caused me to focus on a trait of some female Isonychia that I hadn't really noticed before--that white patch between the eyes. I guess my tendency is to pay more attention to the males because they are often the "gold standard" for the identification of many mayflies. Turns out that the light area on the heads of the Iso females is more common than I thought--I notice it in lots of them now. (I've even seen it mentioned as a trait of some Palearctic species of this genus.) Thanks!

The bad news is that I haven't heard back from Luke yet, and it seems that the females of the three species found in your area probably can't be differentiated beyond genus. Unless the good doctor can tell me something that I haven't found in dichotomous keys, I may not be able to do any better than just Isonychia.

despite the angle, I'm reasonably sure that this is a female Isonychia imago. What's interesting about the angle is that it shows the curious white patch between the eyes. The Isonychia species that I find listed for OK are bicolor, rufa, and campestris (sicca). I was sufficiently intrigued by this specimen to send an inquiry to Luke Jacobus (a top mayfly researcher at Indiana University). I'll get back to you when he responds.

Meanwhile, I'm confident enough about the ID that you could probably put it in the Isonychia section of the mayflies. (Or you could just wait until I hear from Luke.)

what is not cool is the angle, and she's a she so eye morphology can't help either so there's just too little to go on...