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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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Stonefly Species Allocapnia ozarkana (Little Snowflies)

Species Range

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Source: Epiproct And Dorsal Process Structure In The Allocapnia Forbesi Frison, Allocapnia Pygmaea (Burmeister), And Allocapnia Rickeri Frison Species Groups (Plecoptera: Capniidae), And Inclusion Of Allocapnia Minima (Newport) In A New Species Group

Male epiproct. Apical segment of upper limb ca. 183 µm long, swollen basolaterally but not bearing ear-like lobes; median field of apical segment bearing a patch of wave-like spikes ca. 150 µm long and divided along entire length by groove (Figs. 25 - 28); greatest width of apical segment ca. 175 µm, narrowed to 58 µm at apex (Fig. 26). Basal segment of upper limb ca. 343 µm long and ca. 97 µm wide at mid-length; margins of basal segment lacking setae, median groove present, at least in basal half. Lower limb ca. 110 µm wide proximal to apical spoon. Male tergal process. Prominent raised structures on abdominal terga 7 and 8 (Figs. 25, 28 - 30). Process of tergum 7 ca. 72 µm wide and separated to base into a pair of small mounds (Figs. 29 - 30); apices of lobes appear smooth. Process of tergum 8 ca. 188 µm wide and divided to base by gap ca. 50 µm wide (Fig. 30); dorsal surface of lobes covered with scale-like structures.


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References

Stonefly Species Allocapnia ozarkana (Little Snowflies)

Taxonomy
Species Range
Resources
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