The males have these abbreviated wings. I doubt they can fly but they can run faster than any stonefly I have seen. The also have an interesting habit of jumping.

I think this is one of the most poorly understood of the golden stoneflies. It is rare to see any articles about it or fishing the hatch. It emerges late in summer usually on medium to large rivers.The adults are quite secretive but it is something to see the adults run across the water surface. These guys can really run. The males have short wings.The females are up to 1 1/4 inch long rivaling the salmonfly as the largest adult stonefly in the west.The adults are not real golden in color, especially the females which are more of an off yellow to off white abdomen. In handling the adults it is obvious that they shun direct sunlight. I find them by turning over rocks close to the water's edge.

These specimens are either Cheumatopsyche or Hydropsyche. They escaped before I could catch them.I suspect, based on size, they are Hydropsyche, they are about 1/4 inch in length. Both H. occidentalis and H. californica are common in the Touchet River.

Here is the female spinner of the tiny Acentrella turbida. You can see the coloration is quite different from the male.

I would not like to have to match this hatch. These are the smallest mayflies I have ever seen. I used to think Caenis was the smallest adult mayfly in the west but these guys are about 4mm long. The male eyes are two toned, brown above and olive below. The abdomen is dark brown interspersed with light brown. The abdomen is clear for the anterior 2/3rd and the remainder is white. The tails are twice as long as the insect. There is only one pair of wings.

I associated this female with a male I collected one night later. For a great and informative discussion of all Epeorus species and other mayflies be sure and read, WESTERN MAYFLY HATCHES by R. Hafele and D. Hughes. They rate all of the western mayflies and they rate the hatch of this genus a 25 out of a possible 45 points based on several rating criterion. They provide insect photos, possible fly patterns and fly presentations. This is a great book.

Edit by Troutnut: Bob generally knows his IDs better than I do, but I think this one was misidentified as Epeorus longimanus. The darkened humeral crossvein is not supposed to be present in longimanus. I'm moving it up to Epeorus.