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.

The trees were leafing out and the trout were rising on this productive Wisconsin stream

From the Namekagon River in Wisconsin

Stream photos

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Ephemerella mucronata Mayfly Nymph Ephemerella mucronata Mayfly Nymph

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington

This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.

17 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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Hydropsyche (Spotted Sedge) Caddisfly Pupa Pictures

Several users have interesting comments in the discussion of this specimen, but this observation by Creno is especially good:

Also, this is what I would call an "immature" pupa. The wingpads of caddis pupae darken to nearly black as the enclosed adults near emerging. The darkening is the developing adult wing inside the pupal wing pad. The ultimate coloration of the adult wing is not very apparent in most pupal wing pads as the majority of the adult wing coloration comes from the color/position of the adult wing hairs and setae. But dark pupal wingpads are a good indication that the emergence will occur very soon, likely that day or so, and that the adult parts are sufficiently developed within the pupae to make a species determination from the specimen, particularly if it is a male.

Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Pupa from the Delaware River in New York

Lateral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Pupa from the Delaware River in New York

Ventral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Pupa from the Delaware River in New York

Dorsal view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Pupa from the Delaware River in New York

Ruler view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Pupa from the Delaware River in New York The smallest ruler marks are 1 mm.

This caddisfly was collected from the Delaware River in New York on May 13th, 2007 and added to Troutnut.com by Troutnut on May 18th, 2007.

Discussions of this Pupa

Hydropsychid?

14 replies

Posted by GONZO on May 19, 2007

Last reply on May 7, 2009 by LittleJ

This actually looks more like a hydropsychid to me, probably one of the lighter-winged species of Cheumatopsyche. I hope we can get one of the experts to take a look.

Start a Discussion of Pupa

References

Allen RK. 1977. New species of Ephemerella (Ephemerella) from Alberta (Ephemeroptera: Ephemerellidae). The Pan-Pacific Entomologist 53: 286-286.
Jacobus, L. M., Wiersema, N.A., and Webb, J.M. 2014. Identification of Far Northern and Western North American Mayfly Larvae (Insecta: Ephemeroptera), North of Mexico; Version 2. Joint Aquatic Science meeting, Portland, OR. Unpublished workshop manual. 1-176.
Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.