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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.

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 minerva

Where & when

Time of year : June to July

The USGS shows this species in southern Appalachia and the Ozarks, as well as one county in Maine.

In 20 records from GBIF, adults of this species have mostly been collected during July (40%), June (30%), and August (25%).

In 2 records from GBIF, this species has been collected at elevations of 236 and 981 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

Described in Needham et al (1935) as Heptagenia minerva
Body length: 6 mm
Wing length: 7 mm

Face pale yellow with black markings along anterior margin; no ruddy shading on vertex. Thorax pale lemon yellow; a geminate brown mid-dorsal line on the anterior portion of mesonotum, and two small black dots laterally at base of scutellum. A broad blackish stripe on pleura above the leg bases. Legs pale yellow; fore femora with a median ruddy streak and an apical black longitudinal dash on the ventral edge; other femora with similar dark apical dash, but median band may be absent. Fore tarsus and apical half of fore tibia smoky. Basal tarsal joint 1/4 to 1/6 of second. Wings hyaline; longitudinal veins fine, dark; cross veins heavier, margined in the costal and subcostal spaces, those at bulla with margins sometimes coalescing; veins below bulla and brown cloud on posterior branch of radial sector, as in H. hebe (now a synonym of Leucrocuta hebe) and H. aphrodite (now a synonym of Leucrocuta aphrodite) 3 to 4 costal cross veins before the bulla.

Abdomen pale yellowish white, tergites 8-10 tinged with ruddy brown. The lateral brown markings of the tergites are restricted to a series of lateral dashes or small triangular patches. Sternites unmarked. Forceps and tails pale. Apical projection of penes less prominent than in H. aphrodite.

The pale thorax with dark mid-dorsal line on mesonotum anteriorly, the two dark dots before scutellum, the ruddy median streak on fore femora and the much restricted lateral abdominal markings separate this species from the closely allied H. aphrodite.

Start a Discussion of Leucrocuta minerva


  • Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.
  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Leucrocuta minerva

Species Range
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