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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

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.

Artistic view of a Perlodidae (Springflies and Yellow Stones) Stonefly Nymph from the Yakima River in Washington
This one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.
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 gregalis (Blue Quills)

This species produces fishable hatches, but it is not well-known in angling literature. This is due primarily to its range, which consists only of California and parts of Oregon. It is a small (by western Paraleptophlebia standards) Spring emerger that fills the niche taken by Paraleptophlebia heteronea in the rest of the West.

Where & when

Time of year : March through May; best in April and May

In 8 records from GBIF, adults of this species have been collected during June (63%), July (25%), and April (13%).

Species Range

Nymph biology

Environmental tolerance: Tolerant of warm water

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: 8 mm
Wing length: 8-9 mm

A reddish brown species with the thorax blackish above. Fore legs reddish brown except the tarsi which are paler, as also are middle and hind legs. Wings hyaline with the longitudinal veins a little tinged with brown as are also the cross veins of the stigmatic area. The latter are irregular, somewhat branching, twelve to sixteen in number.

Abdomen brownish with darker lines across the joinings of the middle abdominal segments. Tails dingy whitish, becoming ferruginous basally. The long joint of the forceps is conical at base and parallel sided for half its length, then slowly tapering to the apex. The third joint is about half as long as the second. The broadly U-shaped notch between the penes is almost closed by a pair of hyaline, oblong, broad, flat, obliquely converging lobes that extend most of their length beyond the chitinized tip. They thus give the cleft a flask-shaped outline (see fig. 133). External to these the apex is obliquely truncate, the shorter external angle ending in a sharp backwardly-directed tooth. The reflexed spur is hyaline, semi-elliptical with a straightish external and a convex internal margin and rather acute apex. It is a little longer than the middle cleft is deep. The lobes of the divided tenth sternite are very broadly triangular and rounded on the ends.

Described as P. invalida

Body length 6-7 mm, wing length 7 mm

This is an all brown species, with faintly-ringed abdomen. Thorax shining brown above and beneath a little paler on the sides before the wing roots and about the leg bases. Legs nearly uniform, paler brown only a little darker on the fore femora and knee joints. Wings hyaline, the membrane iridescent, the three long veins of the front brown, the others nearly colorless, as are all the cross veins except those of the stigmatic area. These are about ten in number, simple and oblique.

Abdomen brown, only a little paler below, and narrowly on the joinings of the middle segments. Segments 7 to 10, darker; forceps and penes paler. The cleft between the penes is linear U-shaped. The pale end lobe and the external end tooth are minute, and the reflexed spur is short, with an outcurving acute point (see fig. 135). Tails very pale brown, with very faint indication of darker joinings on basal segments.

Start a Discussion of Paraleptophlebia gregalis


Mayfly Species Paraleptophlebia gregalis (Blue Quills)

Species Range
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