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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 Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
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 Paraleptophlebia moerens

Where & when

In 13 records from GBIF, adults of this species have been collected during June (69%), May (15%), July (8%), and April (8%).

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: 6 mm
Wing length: 6 mm

This is another small, clear-winged species with whitish, cross-lined abdomen. Head and thorax dark brown above. Legs pale. Wings whitish with a milky stigmatic area covering costal and subcostal interspaces. Costal cross veins almost wholly obsolete even in the stigmatic area where their faint vestiges are numerous, simple, and considerably aslant.

Abdomen brown on the ends; segments whitish on 3 to 6; less so on 2 and 7. The dorsal apical cross-bands of the white segments are well marked, as are also the lateral, longitudinal, spiracular lines which meet them at the hind angle of the segments. Forceps with a large basal lobe-like dilatation of its first segment. Penes separated for half their length by an oval notch, the aperture of which is closed by a lobe-like prolongation inward of their distal ends. Outer angle of the tips broadly rounded. The proximal portion of its margin is prolonged forward in an incurved spine; attached to this spine is the usual reflexed spur which is very slender (see fig. 133). Tails white.


Start a Discussion of Paraleptophlebia moerens

References

  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Paraleptophlebia moerens

Species Range
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