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3. Yakima River Light Cahill

Hi Roger, sorry to start a new thread on this topic, but couldn't figure out how to post more pics. Bruce.

Hi Bruce-


My guess would be that the imago in the lower right corner of your 2nd photo may be of genus Epeorus.

Bruce-

I wonder if your nymph might be a Cinygmula or Cinygma species,see the links below.

For Cynigmula: http://www.troutnut.com/specimen/980

For Cynigma: http://www.troutnut.com/specimen/968

Thanks Roger and Mark, will try to shoot better photos next year. What bits are important to include in the photos? The spring and fall Cahills appear to be the same mayfly, but perhaps not. Could the offspring from the spring Cahills mature in time to emerge in the fall? I'm pretty sure that the emergers and duns in the pump samples were the same bug, no other mayflies were emerging on that day.

Bruce-

Not likely, as I the western Cahills are uni-voltine. However, there are different Cinygmula species emerging from early May through at least the end of September. One example of this would be Cinygmula ramaleyi, a mid-spring to early summer emerger, and Cinygmula reticulata, a mid-summer to early-fall emerger.

Bruce-



If possible with the nymphs a complete ventral and dorsal photo, and a close up of the gills, also a close up of the head.

You might want to keep the nymph to send to someone who could take a look at it. Just plunk it in some alcohol.

Hi Bruce,

I'm a bit late in replying to this one, but I would mainly just second what Roger said. It looks like Cinygmula or Cinygma. Species identification within these groups can be tricky. To tell the two genera apart, the most helpful shot would be a closeup dorsal view of a live, intact nymph, especially the head. Cinygmula has mouthparts that conspicuously stick out to the sides of the head when viewed from the top.