Blue-winged Olives
Baetis
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.
- The prosternal horn is present.
- The mandible is clearly toothed, not formed into a uniform scraper blade.
- The seems to be only 2 major setae on the ventral edge of the hind femur.
- Chloride epithelia seem to be absent from the dorsal side of any abdominal segments.
Based on these characteristics and the ones more easily visible from the pictures, this seems to be Grammotaulius. The key's description of the case is spot-on: "Case cylindrical, made of longitudinally arranged sedge or similar leaves," as is the description of the markings on the head, "Dorsum of head light brownish yellow with numerous discrete, small, dark spots." The spot pattern on the head is a very good match to figure 19.312 of Merritt R.W., Cummins, K.W., and Berg, M.B. (2019). The species ID is based on Grammotaulius betteni being the only species of this genus known in Washington state.
Mayfly Species Caudatella edmundsi
Species Range
Identification
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.
Nymph
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
References
- 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.
Mayfly Species Caudatella edmundsi
Species Range
Resources
- NatureServe
- Integrated Taxonomic Information System
- Global Biodiversity Information Facility
- Described by Allen (1959)