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.
Specific collection sites for Ephoron leukon
Specific collection sites for Ephoron leukon
The specific collection location data from this map were pulled from the Global Biodiversity Information Facility (GBIF) website under the Creative Commons license. Data there come from a variety of sources, some of which are populated by hobbyists. Both the precision of the location and accuracy of the identification could be low. This map is not an authoritative scientific source, nor an exhaustive list of everwhere this taxon is found, but it should be good enough for anglers. Click each marker on the map for more information about that report, including a link to more details on GBIF.