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 Leucrocuta thetis
Species Range
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
Wing length: 9 mm
A species of the maculipennis group (now a synonym of Leucrocuta maculipennis); very similar to H. juno (now a synonym of Leucrocuta juno), but with no dark marks on pleura.
Head pale yellowish white; a large smoky spot on each side of vertex between eye and lateral ocellus. Thorax yellowish; no dark longitudinal marks above leg bases, as in other species of this group. Legs pale yellowish; a short black streak apically on ventral margin of fore femur, not evident on other femora. Costa, subcosta and radius of fore wing pale amber; other longitudinal veins hyaline. Cross veins in anterior half of fore wing blackish; all others hyaline. Basal costal cross veins and a few in subcostal and third space slightly thickened; two cross veins at bulla in each of first three spaces; stigmatic cross veins finer and fainter than in H. juno, and more numerous ( 11 to 13 in thetis, 8 to 9 in juno). Abdomen pale whitish; segments 2 to 6 and basal portion of 7 semi-hyaline; apical segments opaque, light red-brown dorsally, somewhat paler ventrally. Posterior margins of tergites narrowly purplish black, most evident in dorsal portion. Tails whitish, unmarked. Genitalia much as in juno; penes with more distinct apical lobe, and longer spine on inner apical margin (see fig. 96).
Female very similar to male, aside from usual sex differences.
Nymph
Start a Discussion of Leucrocuta thetis
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.
- Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.
Mayfly Species Leucrocuta thetis
Species Range
Resources
- NatureServe
- Integrated Taxonomic Information System
- Global Biodiversity Information Facility
- Described by Traver (1935)