This is one of four specimens I photographed together from the same hatch, also including a nymph, a male dun, and a female dun. According to the key in Check (1982), the clear wing venation on the associated dun shows that it is either Callibaetis ferrugineous or Callibaetis pallidus, and the characteristics to tell the difference between those two are maddening for both the nymph and adult. If the partial shading in the wing is "medium to dark brown," and the dots on the body are "fuscous to dark brown," then it's ferrugineous. If the wing shading is "chestnut brown" and dots on the body are "yellowish to chestnut brown," then it's pallidus. However, several spare specimens I collected alongside the one in the photo have no markings on the wing at all, which would seemingly indicate ferrugineous according to the key. It's enough for a contingent ID, but I still wouldn't rule out pallidus.
A problem with many Alaskan adventures is that they're too logistically complicated to be done on very short notice, but planning ahead locks one into the unknown weather conditions on the planned dates. This hunting season, my dad was visiting to help with work (he became my unpaid field technician weeks after retiring from a supervisory position in the Wisconsin DNR) and to accompany me on my annual caribou hunt. Our tight schedule for work and play allowed no time to wait for pleasant weather or positive hunt reports. The forecast predicted days of cold rain. People were seeing very few caribou near the Denali Highway, but a few nice bulls were reportedly secluded many miles back high in the Clearwater Mountains in the central Alaska Range.
Just before noon on Wednesday, August 27th, we set out for those distant mountains in hopes of finding bulls. We planned to hike about twelve miles in, skirting the toes of ridges through the alpine tundra just above dwarf birch and willow thickets that stretched out below for dozens of miles. We carried rolled-up packrafts, including my fifteen-pound PR-49 for hauling meat and a rented five-pound Alpacka Denali Llama) for my dad. We would exit by floating fifteen miles down Clearwater Creek to the highway, a gentle and uneventful ride according to inaccurate reports.
Carrying 70-pound packs laden with rafting gear and several days of food, hunting, and camping supplies, we bushwhacked a mile uphill to reach the easier walking on the high tundra. Light but relentless rain chilled the forty degree air. Everything was wet, and as we busted through thickets the water found its way between garments and in places pressed through the fabric of our top-notch breathable Kuiu raingear through the combined efforts of a thousand wet twigs and leaves.
Caribou sightings lifted our spirits. The first cow and calf appeared on the first alpine tundra ridge above the road. We planned to skirt this ridge and several others by hugging the boundary between alpine and scrub tundra, giving us a reasonably high vantage point with relatively level walking. In the next couple valleys between ridges we spotted about twenty caribou, all cows and calves except for one young bull with a rack no larger than a cow's. My goal for this trip was to finally get a big, mature bull, so I let these animals pass without a second thought.
We camped for the night about six miles in, after ascending a long shelf of tundra on the side of a mountain up to an elevation of 3700 feet. Tents were pitched in light rain, and we had no trouble falling asleep at 9:00 pm.