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.
In 1874 records from GBIF, adults of this genus have mostly been collected during June (26%), July (22%), May (17%), August (17%), September (7%), and April (6%).
In 802 records from GBIF, this genus has been collected at elevations ranging from 3 to 13671 ft, with an average (median) of 2723 ft.
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.