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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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Stonefly Genus Amphinemura (Tiny Winter Blacks)

Where & when

In 96 records from GBIF, adults of this genus have mostly been collected during May (36%), April (27%), and June (26%).

In 9 records from GBIF, this genus has been collected at elevations ranging from 480 to 3264 ft, with an average (median) of 2917 ft.

Genus Range

Specimens of the Stonefly Genus Amphinemura

1 Female Adult

Start a Discussion of Amphinemura

References

Stonefly Genus Amphinemura (Tiny Winter Blacks)

Taxonomy
Species in Amphinemura: Amphinemura varshava
15 species (Amphinemura alabama, Amphinemura apache, Amphinemura appalachia, Amphinemura banksi, Amphinemura delosa, Amphinemura linda, Amphinemura mexicana, Amphinemura mockfordi, Amphinemura mogollonica, Amphinemura nigritta, Amphinemura puebla, Amphinemura reinerti, Amphinemura texana, Amphinemura venusta, and Amphinemura wui) aren't included.
Genus Range
Common Name
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