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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.

Dorsal view of a Kogotus (Perlodidae) Stonefly Nymph from Mystery Creek #199 in Washington
This one pretty clearly keys to Kogotus, but it also looks fairly different from specimens I caught in the same creek about a month later in the year. With only one species of the genus known in Washington, I'm not sure about the answer to this ID.
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 Leucrocuta umbratica

Where & when

In 4 records from GBIF, adults of this species have been collected during June (75%) and August (25%).

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

Described in Needham et al (1935) as Heptagenia umbratica
Body length: 7-8 mm
Wing length: 8-9 mm

Mesonotum brown; abdominal tergites 2-6 pale yellow, posterior margins black, with brown lateral patches; genitalia as in fig. 95.

Frontal portion of head light yellow; frontal shelf semi-hyaline with a blackish streak; vertex brown. Thoracic notum and pleura brown; sternum light yellow. Legs pale yellowish, with scattered black streaks at their bases; fore femur slightly deeper yellow, fore tibia and tarsus smoky; basal joint of fore tarsus about 1/5 of the second, which is slightly shorter than the third. Wings hyaline; longitudinal and cross veins in costal half of fore wing brownish, all other veins pale; 3 to 4 basal costal cross veins.

Abdominal segments 2-6 light yellow, semi-hyaline; tergites narrowly black on the posterior margins, and with brown triangular submedian lateral patches based on the posterior margin, the apex rather blunt and not quite reaching the anterior margin. Segments 7-10 opaque; tergites brown, with the dark lateral patches faintly indicated; sternites shaded with brown. Forceps creamy, tinged with brown basally. Tails whitish, unmarked. Penes distinctly reminiscent of the maculipennis (now a synonym for Leucrocuta maculipennis) group, although the lack of shading on the cross veins separates it from species of that group.

Start a Discussion of Leucrocuta umbratica


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

Mayfly Species Leucrocuta umbratica

Species Range
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