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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Limnephilidae (Giant Sedges) Caddisfly Larva from the Yakima River in Washington
This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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149113 has attached these 7 pictures to aid in identification. The message is below.
149113
Pennsy

Posts: 3
149113 on Jul 21, 2016July 21st, 2016, 9:45 am EDT
Found these two around Middletown, PA last evening. Both spinners with one spent and one upright. Looking at the previous posts it would seem these are female? These measured 27mm. Previous post seem to indicate Hexagenia bilineata
Taxon
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Site Editor
Plano, TX

Posts: 1311
Taxon on Jul 21, 2016July 21st, 2016, 9:42 pm EDT
Hi Bob-

Welcome aboard. Yes, I believe the first two photos to be Hexagenia bilineata female imagoes. I believe the others to be Hexagenia female subimagoes of undetermined species.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Crepuscular
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Boiling Springs, PA

Posts: 920
Crepuscular on Jul 22, 2016July 22nd, 2016, 7:48 am EDT
Yes sir. Like Roger said that's H bilineata. big girls! Thanks for posting.

Eric
149113
Pennsy

Posts: 3
149113 on Jul 22, 2016July 22nd, 2016, 8:44 am EDT
Thanks guys! I shot a few pics of one last evening and added those to the original post... couldn't figure out how to add them to a separate post. Looking at other ID's these seem like Hexagenia limbata but just wanted to confirm. This specimen measured 24.5mm and was a subimago. It was just hanging out near a light fixture with a lot of smaller mayflies
Jmd123
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Oscoda, MI

Posts: 2474
Jmd123 on Jul 22, 2016July 22nd, 2016, 10:58 am EDT
I love anything Hexagenia. The guys who flyfish the Huron River for smallies downstate love this hatch, and this is when they show up, into August too. Didn't get enough of Hex mania in June? Well here's another chance...

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
Crepuscular
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Boiling Springs, PA

Posts: 920
Crepuscular on Jul 23, 2016July 23rd, 2016, 2:52 am EDT
Looking at other ID's these seem like Hexagenia limbata but just wanted to confirm. This specimen measured 24.5mm and was a subimago. It was just hanging out near a light fixture with a lot of smaller mayflies

I'd call that H. limbata. And I have collected them together with H. bilineata from the Susquehanna River.
149113
Pennsy

Posts: 3
149113 on Jul 23, 2016July 23rd, 2016, 9:09 am EDT
Looking at other ID's these seem like Hexagenia limbata but just wanted to confirm. This specimen measured 24.5mm and was a subimago. It was just hanging out near a light fixture with a lot of smaller mayflies

I'd call that H. limbata. And I have collected them together with H. bilineata from the Susquehanna River.


Thanks! I saw some of the white flies last evening down by the park on the river. Considerably smaller than these hex mayflies but there were a lot of them

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