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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 Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
This specimen appears to be of the same species as this one collected in the same spot two months earlier. The identification of both is tentative. This one suffered some physical damage before being photographed, too, so the colors aren't totally natural. I was mostly photographing it to test out some new camera setting idea, which worked really well for a couple of closeups.
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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Lateral view of a Female Ephemera varia (Ephemeridae) (Yellow Drake) Mayfly Spinner from Cayuta Creek in New York
I found this female spinner ovipositing in a small stream. She came along while I was playing a trout -- every good bug seemed to do that last night! I didn't have my bug net, so I caught the trout in my landing net, released the trout, and caught the mayfly in my landing net. Her wing got a bit messed up from that.
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Jul 10, 2006July 10th, 2006, 2:47 pm EDT
Not sure who (originally) came up with a 13-16 mm. length range for Ephemera varia spinners, but I'm suspecting each subsequent author must have just parroted it. Your specimen appears to be 19 mm. in length, and there is certainly no doubt concerning its identity.
Best regards,
Roger Rohrbeck
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Sep 13, 2006September 13th, 2006, 5:07 am EDT
I agree with Taxon that the size range for the yellow drake is regularly underestimated. On the Yellow Breeches, they typically range 16-18mm for the males and 17-20mm for the females. All of the large burrowers are quite variable in length, and the size of brown drakes (E. simulans) is similarly underestimated in some texts. My largest specimens of varia are from large limestone waters (like the Breeches), and the largest simulans specimens were found in lake-dwelling populations.

On a related note, I find that the size range of slate drakes (I. bicolor) is also frequently low-balled.

I have collected specimens of all three species that were in the (+/-)20mm range.
Troutnut's profile picture
Bellevue, WA

Posts: 2758
Troutnut on Sep 13, 2006September 13th, 2006, 5:24 am EDT
20mm for all three of the species that were rolled into Isonychia bicolor? Wow, you've got some big ones. I've found them mostly from 12-15mm in upstate NY, but I could imagine another 5mm in your spring creeks. I've probably caught them up to 16-17mm on the Namekagon in Wisconsin, but that's the biggest I've seen them. On that river they're surface emergers of the variety formerly known as sadleri.

You're definitely right that they're frequently underestimated. I've only been in one fly shop that had Isonychia dries as large as the real insects. I've done well tying my own on size 8 hooks. Mostly I find them in shops at size 12.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Sep 13, 2006September 13th, 2006, 5:46 am EDT

Sorry for confusing the subject with my last sentence, but I actually meant that I have collected specimens of E. varia, E. simulans, and I. bicolor in the 20mm range. However, since former designations like sadleri and harperi are now synonymous with bicolor, I suppose there's nothing wrong with your interpretation of what I was trying to say! Anyway, the big slate drakes I was referring to did not come from local limestoners (where they are a fairly minor hatch); instead, they were from my old home-waters on the lower Brodhead!

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