Millcreek on Jan 24, 2015January 24th, 2015, 1:07 pm EST
This mayfly was collected from the Russian River near Healdsburg, Ca. It's common from March through October. It's usually found in shallow water 3-12 inches deep and relatively free of silt with a bottom of sand, gravel and cobble.
It's fairly easy to identify from the dorsal side of the abdomen with section five, nine and ten being mostly light in color. It's also got a mouth with labial palpi having the inner margin of segment 2 slightly convex to nearly straight as opposed to variously concave. It also has the first gill much smaller than the others.