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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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Mayfly Species Cinygmula gartrelli

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.

Male Spinner

Body length: 9 mm
Wing length: 10 mm

Male. Eyes (dried) deep black-brown, not contiguous. Head with anterior portion sepia-brown with paler antennal pits and some black shading on each side of the vertical keel; vertex of head behind the ocelli deep blackish. Thorax dorsally sepia-brown, shading into black-brown on mesonotum posteriorly and with lighter shades on anterior projection of mesonotum and faintly cephalad of scutellum; pleura brown, with the membranous portions paler, a wine-colored patch anterior to base of forewing from which a pale ochreous dash projects towards the pronotum; there are also faint ruddy tinges at bases of legs; sternum brown, shaded with black brown. Abdomen dorsally with segment I deep brown, segments II-VII with anterior half pale, semi-hyaline ochreous-brown, the posterior portion deeper brown with a slight ruddy tinge, giving a distinct banded appearance; segments VIII-X opaque, more evenly dark brown with the paler areas showing as small lateral patches on VIII and IX. Ventrally light ochre-brown, faintly tinged with ruddy along posterior margins and at times on three posterior segments; ganglionic marks very faintly visible. Forceps and setae deep smoky. Forelegs deep smoky-brown, tibia slightly longer than combined trochanter and femur; mid and hind legs paler brown with slight ruddy tinge on the femora. Wings very characteristically marked, hyaline with a brownish-amber tinge at base, extending more faintly along costal region of both wings; veins fine, brown; crossveins strong, brown, lightly bordered in the costal half of forewing with brown shading which gives them a decidedly thickened appearance in this region.

Female Spinner

Body length: 9 mm
Wing length: 10 mm

Slightly paler than male. Head light brown, shaded with ruddier brown next the eyes. Pleura and abdomen with more extended ruddy brown suffusion than in the male. Forelegs paler.


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References

Mayfly Species Cinygmula gartrelli

Species Range
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