Please identify this mayfly

I would say family Baetidae (I call them Baetis, many call them Blue Winged Olives). Not sure on the Genus, but someone more qualified may be able to tell from the picture.

As a side note, I think Blue Winged Olive being used for Baetidae is misleading, as I believe the original "Blue Winged Olive" common name was used to identify some mayflies from the Ephemerellidae family. Additionally, while the Baetidae in my area are in most cases light Olive, a recent trip to the Green River in Utah showed me that the Baetidae in that area are mostly gray.

Like @Triggw said, fish a size 20 or 22 parachute with some white microfibbets, a light gray/cream body, dark thorax, and light dun Hackle.
 

Paraleptophlebia mollis male spinner

Fly Fishing Gallery
www.riseformsflyfishing.com

Used to run into them fishing Big Hunting Creek in Maryland back in the 90’s; mostly the duns, #16-18 (western ones smaller?), not the spinners like the pic you posted. Never hit a heavy hatch but the fish seemed to like them; think I used a grey bodied Hairwing Dun.

Regards,
Scott
 
Scottp said:

Paraleptophlebia mollis male spinner

Fly Fishing Gallery
www.riseformsflyfishing.com

Used to run into them fishing Big Hunting Creek in Maryland back in the 90’s; mostly the duns, #16-18 (western ones smaller?), not the spinners like the pic you posted. Never hit a heavy hatch but the fish seemed to like them; think I used a grey bodied Hairwing Dun.

Regards,
Scott
Click to expand...

Scott -

That picture sure makes it look like you nailed it, they look identical!

Definitely not trying to start an argument, but now you got my curiosity going. I notice the picture from that link is from PA, and I don't see that species being present in the Northwest in any of the texts. I also think it's possible that the picture from your link is incorrectly identified. I believe that to be a Baetidae as well. From Merrit and Cummins key, family Leptophlebidae have 3 tails (cerci).

Paging @Taxon and @Mark Melton.
 
Scott, I too fished big hunting creek in the 90s. I am a fighting terrapin, did my major in fisheries management and my minor on aquatic ent in fishing creek, right next door!
 
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Does the pictured spinner have a malformed third (middle) tail? What’s that little loop thing there?
 
James,

Appreciate your take on the bug in question. I’d be curious to hear what the bug guys have to say, too.

Regards,
Scott
 
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Great replies, thanks guys! James, I was leaning toward bwo’s as well, but the coloration just didn’t seem right.

Scott, that pic of the paraleptophlebia sure seems to be right on the money.
I encounter them in just a few waters in my area (SW Idaho), but see these “Mahogany Duns” in the fall, whereas I believe I took this photo in the summer. (I could be wrong, I took this photo years ago).

Paraleptophlebia | Idaho Fish and Game

idfg.idaho.gov idfg.idaho.gov

Also, the (excellent) book Western Mayfly Hatches by Hafele and Hughes states that Mahogany Duns have 3 tails, not 2 as in my photo.

So, for me, the jury is still out …
 
Taxon said:
Hi Mark-

I believe there is actually at least one Anafroptilum species present in Idaho. Please see Anafroptilum bifurcatum.
Click to expand...
Yeah, apparently there is. I was going by Idaho's Fish and Game guidebook which says there are none in the state. https://idfg.idaho.gov/species/taxa/2011420
Incidentally, your map shows none in Montana. Apparently they have two species of Anafroptilum.

Forky Small Minnow Mayfly - Montana Field Guide

fieldguide.mt.gov fieldguide.mt.gov

Dusky Small Minnow Mayfly - Montana Field Guide

fieldguide.mt.gov fieldguide.mt.gov
 
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