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Free2Fish
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 Posted: Thu Jan 22, 2015 5:26 pm • # 1 |
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Joined: 12/10/14
Posts: 218
Location: Manitoba
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Recently there have been some sporadic hatches of large mayflies on the Guadalupe most afternoons that have attracted some fishy interest. One is the Hexagena Limbata and the other is what I would call a March Brown.  I became interested in what specie this might be and the closest candidate I could find is a Rhithrogena Germanica. Distinguishing features are mottled wings, two tails and a spot on each leg...features that my specimen has. Nice fit, but unfortunately they don't exist on this side of the Atlantic. Anyone out there who can help out a puzzled fisherman? 
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Free2Fish
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Posted: Thu Jan 22, 2015 5:48 pm • # 2 |
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Joined: 12/10/14
Posts: 218
Location: Manitoba
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I think I may have found the answer. It looks like it's the eastern version of our March Brown, Macaffertium vicarium. I found a picture but its copyrighted so I don't think I can copy it to here but here's the link. http://www.troutnut.com/specimen/529If anyone knows different I'd still love to know about it.
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GordoB
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Posted: Thu Jan 22, 2015 8:51 pm • # 3 |
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Joined: 04/29/12
Posts: 71
Location: Tyler, Texas
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I sent the photo to Rob Woodruff, who is an Orvis guide and a graduate entomologist. Here is his reply:
Isonychia Mayfly
Rob Woodruff
Orvis Endorsed Fly Fishing Guide
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Free2Fish
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Posted: Thu Jan 22, 2015 9:46 pm • # 4 |
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Joined: 12/10/14
Posts: 218
Location: Manitoba
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Thanks Gord, appreciate it.
I guess this is Isonychia sicca then, as listed in "Mayflies of the Guadalupe River".
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Free2Fish
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Posted: Fri Jan 23, 2015 9:53 am • # 5 |
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Joined: 12/10/14
Posts: 218
Location: Manitoba
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I'm not wanting to get into any bug wars but another mayfly expert over at BugGuide thought this might be a Stenonema femoratum. This specie is listed in the Guadalupe mayfly treatise.
I've just learned mayfly identification is not necessarily a walk in the park when only equipped with a single photo.
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preast
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Posted: Sat Jan 24, 2015 1:21 pm • # 6 |
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Joined: 09/03/10
Posts: 266
Location: Austin, TX
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Yeah I don't think that's an Iso, but I have seen a few of those in your pic on the Guad. Most of the Iso subspecies have considerably darker forelegs always raised up, and no barring on any of the legs, and have a very mahogany (purplish) hue. They are also opaque looking. I took the 2 pics below about 12 years ago on the Guad. You'll see the dun is quite different from the one in your pic but matches the Isonychia Bicolor in all of my research at the time. You can see the little light colored gloves on the dun in my pic (apparently had the nickname "white gloved howdy"). http://www.troutnut.com/hatch/649/Mayfl ... hogany-Dun. Troutnut has some unbelievable photos if you click through. The nymph explains why a Zug Bug or a large PT nymph works on that river, and they are super fast swimmers. Out of the water, they remind me of the alien from the movie. I know this is the right nymph for the dun pictured because I witnessed a hatch in light rain, and they were hatching slow. They crawl out on rocks on the edge of the river so its not really common for trout to key on the dun, but if you can find fish taking them, you can do well on emerger/dries or cripples.  
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Free2Fish
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Posted: Wed Jan 28, 2015 10:36 am • # 7 |
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Joined: 12/10/14
Posts: 218
Location: Manitoba
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I've tried to use a number of nymphs in the pool near my rental without success. Each evening a few trout will surface feed sporadically but I suspect most are subsurface feeding on nymphs. The early surface feed seems to be on hexes and the stenonema and then quits when the hatch of chironomids and what I think might be PMDs takes off. At that point there is little surface activity and I suspect they are feeding on sub surface forms.
Don't have a net and haven't caught any other mayflies flitting around and turning stones over hasn't turned up anything but really small clingers.
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Taxon
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Posted: Mon Oct 03, 2016 11:59 pm • # 8 |
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Joined: 10/03/16
Posts: 3
Location: Plano, TX
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Free2Fish wrote: Recently there have been some sporadic hatches of large mayflies on the Guadalupe most afternoons that have attracted some fishy interest. One is the Hexagena Limbata and the other is what I would call a March Brown. I became interested in what specie this might be and the closest candidate I could find is a Rhithrogena Germanica. Distinguishing features are mottled wings, two tails and a spot on each leg...features that my specimen has. Nice fit, but unfortunately they don't exist on this side of the Atlantic. Anyone out there who can help out a puzzled fisherman? Yes, I believe this female subimago to be Stenonema femoratum.
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