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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 Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
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 Isoperla (Perlodidae) (Stripetails and Yellow Stones) Stonefly Adult from Salmon Creek in New York
A friend brought me this stonefly to photograph. He found it floating on the surface of a trout stream with its wings in a crippled position.
Posts: 3
IanB on May 5, 2009May 5th, 2009, 6:25 am EDT
Ok all, I am finding this hobie increasingly interesting and exciting. I no longer will just be guessing on the river, but actually selecting flies that best represent the actual bugs I am finding.

Here is another one from yesterday's trip, there are many of these flying around as adult, some size 14, others down to size 18, I grabbed one of the larger ones (just pushing size 14) and got some better macro pictures.

Thanks for the help in identifying this 'small' stonefly (that is my identification at this point anyway). Taken May 4th 2009 in the North Shore of Mass.

I apologize, but although I have re-sized these pictures (way down in some cases) I can not get them to display here. Links are posted instead.



other angle


And another angle

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"Bear Swamp," PA

Posts: 1681
GONZO on May 5, 2009May 5th, 2009, 10:08 am EDT

Your stonefly is a member of the Taeniopterygidae, aka "winter stoneflies" or "willowflies." The smaller stoneflies that you saw might belong to another family, the Nemouridae, aka "spring stoneflies" or "forestflies." The emergence of some members of these two families overlaps at this time of year. (They look much alike, but the nemourids are generally smaller, emerge later, and have shorter second tarsal segments.)

BTW, per your previous thread, the #14 mayfly nymphs in the cup with your damselfly nymph are probably Hendrickson nymphs (Ephemerella subvaria).

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