On a trip last week to the St. Joe, a friend of mine photographed these swarms of mayflies on the rocks of a small feeder creek entering the main river. He and I are curious as to their identity. Any direction is appreciated.
Interesting photos. If you closely examine one of the individuals (as shown below), I'm sure you will conclude (as I have), that rather than being mayflies, they are actually crane flies. It looks to me like this one has its abdomen suspended beneath the water in order to deposit its ova on the underlying rock.
I agree with your insight Roger. I did see a number of crane flies on the main stem St. Joe in the areas where I was fishing, but their body color seemed to be rusty brown. Of course, I was seeing them at dusk while this picture was taken with a flash.
Various species of craneflies exhibit a wide variation in color. Many shades of tan and brow, rusty red and a dark gray are quite common. Here are a couple of pictures, including my overly-fussy imitation.