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.

Firehole River Sunset

From the Firehole River in Wyoming

Stream photos

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Glossosoma (Little Brown Short-horned Sedge) Caddisfly Larva Glossosoma (Little Brown Short-horned Sedge) Caddisfly Larva

Dorsal view of a Glossosoma (Glossosomatidae) (Little Brown Short-horned Sedge) Caddisfly Larva from the Yakima River in Washington

I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae Larvae.

11 Recently Added Photos

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 Baetisca rubescens (Armored Mayflies)

Where & when

In 2 records from GBIF, adults of this species have been collected during May (50%) and August (50%).

Species Range

source

Map of specific collection sites

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

Described in Needham et al (1935)

Body length: 6-7 mm
Wing length: 8-8.5 mm

Abdominal tergites of male imago reddish brown, sternites paler reddish to yellowish brown; both wings flushed with reddish in the basal portions; longitudinal veins brown. (See frontispiece).

Head and thorax rather dark reddish brown. Legs yellowish brown; all joinings of fore leg narrowly reddish brown. Wings hyaline; the basal third and most of the costal margin of the fore wing, and most or all of the hind wing, flushed with reddish; in the hind wing this color is deepest at the base, fading gradually toward the outer margin. Longitudinal veins brown; cross veins pale, almost invisible. Abdominal tergites reddish brown, darker next to the pale pleural fold; sternites paler reddish to yellowish brown. Posterior margins of all segments rather dark reddish brown, most evident on the tergites. Forceps and tails pale yellowish; tail joinings slightly opaque, but not darker than the joints. Genitalia as in fig. 148.

The smaller size and darker legs separate this species from Baetisca carolina, which has the wings flushed with orange rather than with reddish.

Start a Discussion of Baetisca rubescens

References

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