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3. Ironodes sp.

The nymphs are members of the Heptageniidae family and are easily identified to genus. They have only two caudal filaments (tails), which narrows it down to Anepeorus, Epeorus and Ironodes. Anepeorus has interfacing setae on the caudal filaments. Ironodes has no interfacing setae on the caudal filaments . Ironodes has a pair of median tubercles on each dorsal segment while Epeorus doesn't.

While easy enough to identify to genus I've only been able to find a description of Ironodes lepidus by Day in "New Species and Notes on California Mayflies (Ephemeroptera)" (1952). This leaves several species undescribed as nymphs that have been reported as occurring in California. I. californicus and I. nitidus have been reported in California and Mayfly Central lists I. arctus and I. geminatus as possibilities in the northwest United States. If anybody has any knowledge of these larvae info would be much appreciated.

The nymphs are usually found in smaller tributaries of the Russian River.They were collected in riffles or shallow glides with moderate to fast flow and a substrate of large gravel and cobble. They are most common in the spring and and early summer months. When ready to emerge they can be seen on the downstream side of large rocks where they crawl up nearly to the waterline, grasp the rock firmly and molt as subimagos. I had some male adults but never got around to keying them out and haven't been able to find the vial with them in it again.

Jacobus & McCafferty (2002) suggested some color characteristics that might
be useful for species diagnosis, but such characters often are variable or
subject to fading. Leave these at the genus level.

Jacobus LM; McCafferty WP. 2002. Analysis of some historically unfamiliar
Canadian mayflies (Ephemeroptera). Canadian-Entomologist
134(2):141-155.

I figured I wasn't going to get very far attempting to ID these to species. Day gives some minor differences in size and coloration as distinguishing characteristics in "Aquatic Insects of California" but as you mentioned above these seem like they would be variable. Thanks for the info.

Mark