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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Case view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
It's only barely visible in one of my pictures, but I confirmed under the microscope that this one has a prosternal horn and the antennae are mid-way between the eyes and front of the head capsule.

I'm calling this one Pycnopsyche, but it's a bit perplexing. It seems to key definitively to at least Couplet 8 of the Key to Genera of Limnephilidae Larvae. That narrows it down to three genera, and the case seems wrong for the other two. The case looks right for Pycnopsyche, and it fits one of the key characteristics: "Abdominal sternum II without chloride epithelium and abdominal segment IX with only single seta on each side of dorsal sclerite." However, the characteristic "metanotal sa1 sclerites not fused, although often contiguous" does not seem to fit well. Those sclerites sure look fused to me, although I can make out a thin groove in the touching halves in the anterior half under the microscope. Perhaps this is a regional variation.

The only species of Pycnopsyche documented in Washington state is Pycnopsyche guttifera, and the colors and markings around the head of this specimen seem to match very well a specimen of that species from Massachusetts on Bugguide. So I am placing it in that species for now.

Whatever species this is, I photographed another specimen of seemingly the same species from the same spot a couple months later.
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

References

  • 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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