Blue-winged Olives
Baetis
Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
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This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
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Mayfly Family Isonychiidae (Slate Drakes)
See Isonychia for details. It is the only North American genus in this family.
Family Range
Identification
To determine whether a specimen of Ephemeroptera belongs to Isonychiidae, use the Key to Families of Mayfly Nymphs or Key to Families of Mayfly Duns and Spinners.
Specimens of the Mayfly Family Isonychiidae
5 Female Duns
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.
1 Male Spinner
I got several really nice pictures of this spinner. I also collected a female on the same trip.
2 Female Spinners
I collected this female together with a male.
13 Nymphs
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.
These three Isonychia nymphs show the variety within the species from a single day at a single collection site.
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.
5 Streamside Pictures of Isonychiidae Mayflies:
Closeup of some recently emerged Isonychia bicolor nymphs from a small stream.
In this picture: Mayfly Species Isonychia bicolor (Mahogany Dun).
Several Isonychia bicolor nymphs had recently crawled out onto these rocks to emerge, leaving behind their telltale shucks.
In this picture: Mayfly Species Isonychia bicolor (Mahogany Dun).
Here are the empty nymphal cases of Isonychia bicolor mayflies which hatched in early fall in the Catskills by crawling out onto a rock.
In this picture: Mayfly Species Isonychia bicolor (Mahogany Dun).
This is just about the most Isonychia bicolor shucks I've ever seen on the rocks, and appropriately enough they're on the river where Art Flick described them in his Streamside Guide.
In this picture: Mayfly Species Isonychia bicolor (Mahogany Dun).
Discussions of Isonychiidae
Isonichya Bicolor
21 replies
Posted by CraigK on Mar 26, 2012
Last reply on Mar 29, 2012 by Entoman
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
Are Isonychia mayflies technically multibrooded?
4 replies
Last reply on Apr 17, 2009 by GONZO
Here's what I've written in my article on Isonychia about their hatching:
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.
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.
Penns Creek Slate Draker's
4 replies
Last reply on Sep 23, 2007 by Shawnny3
Penns is one of the few places where a #10 iso will nail em' all year long
Iso
1 replies
Posted by JMV on Sep 21, 2006 in the species Isonychia bicolor
Last reply on Sep 21, 2006 by Troutnut
Great site, I'm an Iso. fanatic... JM
Start a Discussion of Isonychiidae
Mayfly Family Isonychiidae (Slate Drakes)
Taxonomy
Genus in Isonychiidae
IsonychiaLeadwings
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Genus in Isonychiidae: Isonychia