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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.

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 Baetis rusticans (BWOs)

Where & when

In 5 records from GBIF, adults of this species have been collected during June (40%), May (20%), July (20%), and August (20%).

In 3 records from GBIF, this species has been collected at elevations of 410, 607, and 1112 ft.

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: 3.5 mm
Wing length: 4 mm

Abdominal tergites 2-6 of male imago olive brown, the posterior margins deeper ruddy brown; genitalia of the Baetis intercalaris type, the tubercle on the inner apical margin of the first forceps joint well developed.

Turbinate eyes moderate, red-brown. Head and thorax deep olive brown. Anterolateral margins of the mesonotum paler, “at times terminating in a small yellowish spot on each side of the anterior tubercle”; posterior portion of mesonotum with lateral and central tinges of ruddy brown, the scutellum sometimes paler. Ochreous markings on the pleura. Anterior projection of metanotum whitish. Legs pale yellowish brown; femora, especially near the apex, tinged with deeper brown. Wings hyaline, cross veins slightly brown-tinged. Cross veins of the stigmatic area of the fore wing 4-6 in number, with slight granulations between them. First pair of intercalaries short or obsolescent, second pair shorter than the third. Hind wing about two and one-half times as long as its width; third vein extends weakly to the middle of the hind margin, at the base bent strongly toward vein 2. No intercalaries.

Abdominal tergites 2-6 semi-translucent, olive brown, the posterior margins narrowly deeper, ruddier brown; 7-10 opaque russet brown. Sternites 2-6 smoky hyaline; 7-9 whitish with brown tinges, the posterior margins edged with reddish brown. Tracheae of the stigmatic area form a black lateral line. Tails and forceps whitish. The tubercle on the inner apical margin of the first forceps joint is well developed.

Distinguished from B. levitans (now a synonym of Baetis flavistriga) by the better development of the tubercle on the first forceps joint, and the much darker abdomen. The smaller size, and lack of intercalaries in the hind wing, separate it from Baetis brunneicolor .


Start a Discussion of Baetis rusticans

References

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

Mayfly Species Baetis rusticans (BWOs)

Taxonomy
Species Range
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