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.

Stream photos

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Holocentropus Caddisfly Larva Holocentropus Caddisfly Larva

Dorsal view of a Holocentropus (Polycentropodidae) Caddisfly Larva from the Yakima River in Washington

This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their 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 Rhithrogena manifesta

Very little has been written about this species and I have found no accounts of fishable hatches.

Where & when

Time of year : June-July

In 5 records from GBIF, adults of this species have been collected during July (80%) and June (20%).

In 2 records from GBIF, this species has been collected at elevations of 23 and 26 ft.

Species Range

source

Map of specific collection sites

Nymph biology

Current speed: Fast

Substrate: Gravel

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 manifesta

Body length: 4-7 mm
Wing length: 5-7 mm

Mesonotum piceous; abdominal tergites ferruginous; venation pale hyaline, bases of three main costal veins fuscous at base; type of genitalia uncertain.

Eyes brown above, the lower portion fuscous. Thoracic notum generally piceous. Legs pale greenish; femora with a narrow median band, the knee fuscous; apex of fore tibia, tips of tarsi, and joinings of fore tarsus, fuscous. Wings hyaline; venation pale greenish hyaline, except the basal third of costa, subcosta and radius, and occasionally their tips also, which are fuscous. Abdominal tergites ferruginous, the posterior half or third of each somewhat piceous. Forceps pale; tails uniformly whitish; penes blackish, according to Hagen.

Start a Discussion of Rhithrogena manifesta

References

Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.
Leonard, Justin W. and Fannie A. Leonard. 1962. Mayflies of Michigan Trout Streams. Cranbrook Institute of Science.
Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.