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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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This topic is about the Insect Order Odonata-Anisoptera

Dragonflies and damselflies are in the same order, Odonata, but they are taxonomically separated on an obscure level not built into this site, the suborder. Dragonflies are in the rarely mentioned suborder Epiprocta, and within that suborder is the infraorder Anisoptera, the scientific name by which they're best known. None of that will help you catch trout, but it explains what the hyphen in this page's name is all about.

Example specimens

DMM
Posts: 34
DMM on Nov 26, 2006November 26th, 2006, 4:39 pm EST
This goes for all Gomphidae. If the prementum is flat, and the animal has 4 segments in each antenna, and two-segmented fore and middle tarsi, and a ligula with no median cleft--Gomphid. The Corduligastridae have a spoon-shaped prementum and a cleft in the middle of toothlike processes on ligula. Now you'll know whenever you catch more Odonata.
David
Troutnut
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Bellevue, WA

Posts: 2758
Troutnut on Nov 29, 2006November 29th, 2006, 5:50 am EST
Thanks, I'll keep that in mind when I'm collecting new specimens. One of my goals for next spring is to take a lot more photos of dragonflies and other invertebrates outside the "big three" orders of mayflies, stoneflies, and caddisflies.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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