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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.

Artistic view of a Perlodidae (Springflies and Yellow Stones) Stonefly Nymph from the Yakima River in Washington
This one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.
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 Caudatella edmundsi

Species Range


To determine whether a specimen of Caudatella belongs to Caudatella edmundsi, use the Key to Species of Caudatella Nymphs.

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.

Body length: 7–7.5 mm

Cerci 5-6 mm; terminal filament 8-9 mm. General color uniformly light brown. Head without occipital tubercles; labrum hairy and deeply emarginate (fig. 22); maxillae with very small palpi or palpifer (fig. 20). Legs short and thick, all segments with short heavy spines and only scattered hairs; tarsal claws with double row of denticles, anterior row with 10-14 small denticles and posterior row with 9-12 larger denticles (fig. 21). Abdomen with conspicuous, paired dorsal submedian tubercles on segments 1-10 as in fig. 27; width between bases of tubercles narrow on segment 1, gradually increasing in width to segment 5, narrowing again to segment 10, tubercles barely discernible on segment 10; sterna 4-8 with pale, sometimes obscure, brown dashes on lateral margins (fig. 10). Caudal filaments light brown, lateral cerci 55% to 65% as long as terminal filament.

Specimens of the Mayfly Species Caudatella edmundsi

1 Female Dun
1 Nymph

Start a Discussion of Caudatella edmundsi


  • Allen, R.K., and Edmunds, George F. Jr. 1961. A Revision of the Genus Ephemerella (Ephemeroptera: Ephemerellidae) II. The Subgenus Caudatella. Annals of the Entomological Society of America 54: 603-612.

Mayfly Species Caudatella edmundsi

Species Range
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