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.

Waterfalls over smooth bedrock above Titcomb Lakes

From Titcomb Basin in Wyoming

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington

This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.

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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 Amercaenis ridens (Angler's Curses)

Where & when

In 6 records from GBIF, adults of this species have been collected during July (83%) and August (17%).

In 2 records from GBIF, this species has been collected at elevations of 2592 and 2789 ft.

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.

Female Spinner

Described in Needham et al (1935) as Caenis ridens

Body length: 2.5-3 mm
Wing length: 2.5 mm

This species, known only in the female sex, has a pale yellow mesonotum and pale head, with no dark stigmatic dots.

Head of female whitish; between the rear ocelli is a slightly smoky shading; eyes black, antennae pale. Pronotum whitish with considerable smoky shading. Mesonotum pale yellowish, tinged faintly with brownish, this color rather deeper than in Caenis hilaris; mid-dorsal line faintly dark; posterior portion shaded with smoky; a slight dark streak inward from the wing roots. Two faint dark transverse streaks near the posterior margin of metanotum. Pleura wholly pale except for a small curved dark mark anterior to the base of the middle leg and a slight deepening of color anteriorly. Sternum pale. Fore legs at base, and entire fore femur tinged considerably with smoky; tibia and tarsus paler; width between the leg bases greater than in hilaris. Middle and hind legs wholly whitish, unmarked. Wings semi-hyaline whitish, subcosta and radius purplish.

Abdominal tergites wholly white, except for slight smoky shading laterally on 1 and 2. No traces of dark lateral streaks or stigmatic dots on any segment. Sternites white, unmarked. Tails white, the middle one longer than the laterals.

This species, allied to both C. hilaris and Caenis anceps, is separable from the former by reason of the lack of lateral black dashes on the tergites and the dorsal marks on the femora; from anceps it is distinguished by the paler mesonotum, fewer dark markings on the pleura, the lack of femoral markings, and the presence of slight dark shading on tergites 1 and 2 laterally.