I thought this dun was worth photographing, even though she's in pretty bad shape, because she shows something I haven't seen in Isonychia elsewhere. The bright stripe down the back which is normally present only in the nymph carried over to the dun in this one.
This is a naturally crippled female Isonychia bicolor dun. One of her main wings came out as a deformed, crumpled yellow object. I found her flopped over on her side struggling on the surface of a small stream.
This Isonychia bicolor nymph from the Catskills displays the prominent white stripe sometimes characteristic of its species. This is the first such specimen I've photographed, because members of the same species in the Upper Midwest have a more subdued stripe (and were once thought to be a different species, Isonychia sadleri). The striking coloration on this eastern nymph is more appealing.
This smaller Isonychia nymph was caught with a bunch of bicolor specimens, but it does not have the fluffy spine structure at the base of its gills. This might mean it's Isonychia sayi, or it might just be a bicolor nymph too young to have developed those structures.
I think the Iso. b. female was referred to a generation or so ago as the white gloved howdy. I love those old names. Too bad there are no pics of Potamanthus (golden drake). They may be extinct (siltation and acid rain?)...talked with Charlie Meck about that a few years ago. A beautiful mayfly...an important hatch of years past. I couldn't find any ref. to Epherons. An important hatch for me in about any area of the country. This my first post...love the site...very nice photog. Lets see what the strange weather of the year does to the hatches and fishing for this year. Overall, I expect it can't be good. CK
Here's what I've written in my article on Isonychia about their hatching:
Some Isonychia species are multibrooded, but not in the same way as most other multibrooded mayflies like the Baetidae. In those species, the flies emerging in midsummer or Fall are the offspring of the earlier hatch from the same year. In Isonychia, the Fall emergers are offspring from the previous Fall. They are present as half-grown nymphs when the first of their generation emerge. Although Isonychia broods have distinct peaks, some may be found on the water at any time in between.
I'm curious if they can really be called multibrooded or not, since they don't produce more than one generation per year (as far as I know). They simply have distinct populations within the same generation which emerge at different times during the year. Does that count?
All my books are packed up in boxes right now so I don't have a technical definition of the term handy.