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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

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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Dark Red Quills

Like most common names,"Dark Red Quill" can refer to more than one taxon. They're previewed below, along with 10 specimens. For more detail click through to the scientific names.

Mayfly Genus Cinygmula

These are often called Dark Red Quills.
This is primarily a Western genus. Cinygmula ramaleyi is the most important species, producing good hatches in the West. Cinygmula reticulata may also be relevant, and I have seen a great spinner swarm from an unsung species, Cinygmula par, in the Washington Cascades.

There is only one Eastern species, Cinygmula subaequalis, and its importance is minor.
Lateral view of a Female Cinygmula ramaleyi (Heptageniidae) (Small Western Gordon Quill) Mayfly Dun from Nome Creek in Alaska
This dun is almost certainly of the same species as this nymph, as it hatched in my cooler from a nearly identical nymph.
Lateral view of a Male Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Spinner from the South Fork Stillaguamish River in Washington
I'm unsure of the ID on this one; keys put it closest to Cinygmula reticulata, but I'm very doubtful of the species and not positive on the genus. Epeorus is another possibility, but I don't know which species it would be.

This one was collected in association with a female dun probably of a different family.
Cinygmula ramaleyi (Heptageniidae) (Small Western Gordon Quill) Mayfly Nymph from Nome Creek in Alaska
This nymph is almost definitely the same species as this dun, which hatched from a nearly identical nymph from the same collection.

Mayfly Species Rhithrogena impersonata

These are sometimes called Dark Red Quills.
This intriguing species has two distinct colors of nymphs, which were once considered to be different species. Most nymphs are a dark olive gray, but some are a surprisingly bright reddish brown. The red ones were once classified as Rhithrogena sanguinea. There is no apparent difference between the adults of the two varieties.
Dorsal view of a Rhithrogena impersonata (Heptageniidae) (Dark Red Quill) Mayfly Nymph from Mongaup Creek in New York
This was the only Rhithrogena specimen in a large sample of nymphs from a small Catskill stream. It looks virtually identical to Rhithrogena impersonata specimens collected in the Midwest, but I didn't get to check the distinguishing features under a microscope.

Mayfly Species Rhithrogena jejuna

These are sometimes called Dark Red Quills.

Mayfly Species Attenella attenuata

These are very rarely called Dark Red Quills.
This intriguing species has received a lot of attention in past angling books. Recent authors suspect that much of this credit was a case of mistaken identity, with Attenella attenuata receiving praise for the hatches of Drunella lata and Dannella simplex. Much of the credit was legitimate and accurate, but this species is no longer thought to be on par with its most popular cousins in Ephemerella and Drunella.

I have several specimens listed under this species, but I'm not positive the identification is correct.
Lateral view of a Female Attenella attenuata (Ephemerellidae) (Blue-Winged Olive) Mayfly Dun from the Namekagon River in Wisconsin
This specimen came from the same hatch as a male.

Mayfly Species Isonychia bicolor

These are very rarely called Dark Red Quills.
This is by far the most important species of Isonychia. Many angling books once split its credit with the species Isonychia sadleri and Isonychia harperi, but entomologists have since discovered that those are just variations of this abundant species.

See the main Isonychia page for more about these intriguing mayflies.
Lateral view of a Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Dun from the Namekagon River in Wisconsin
Lateral view of a Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Spinner from the West Branch of Owego Creek in New York
I collected this female together with a male.
Dorsal view of a Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Nymph from the Beaverkill River in New York

Mayfly Species Cinygmula ramaleyi

These are very rarely called Dark Red Quills.
This can be the first mayfly of the season on high mountain streams in the western states, but emerges later in the season in Alaska. It is the most important species of Cinygmula for anglers.
Lateral view of a Female Cinygmula ramaleyi (Heptageniidae) (Small Western Gordon Quill) Mayfly Dun from Nome Creek in Alaska
This dun is almost certainly of the same species as this nymph, as it hatched in my cooler from a nearly identical nymph.
Male Cinygmula ramaleyi (Heptageniidae) (Small Western Gordon Quill) Mayfly Spinner from the Touchet River in Washington
Adults were collected from the North Fork of the Touchet River at Touchet Corral, 21 Sept. One photo is the swarm of males over the stream about 3 PM, air temp about 66 degree.
Cinygmula ramaleyi (Heptageniidae) (Small Western Gordon Quill) Mayfly Nymph from Nome Creek in Alaska
This nymph is almost definitely the same species as this dun, which hatched from a nearly identical nymph from the same collection.

Mayfly Species Rhithrogena undulata

These are very rarely called Dark Red Quills.
This is one of the two most common species of Rhithrogena.
Male Rhithrogena undulata (Heptageniidae) (Small Western Red Quill) Mayfly Spinner from the Madison River in Montana
This male was collected at the same time as this female and is likely the same species.

It keys pretty clearly to Rhithrogena undulata using the key in Traver 1935, although the size is larger than expected for that species in that source.

References

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