Peter discovered this mayfly going through its final molt in his kitchen. It must have flown into his house, which may give you pause, how did it have wings before its final molt? Mayflies are the only insects where a winged form undergoes a further molt. When they first emerge from the water they are commonly called a dun (scientifically called the subimago stage). As duns, mayflies physically resemble the final adult stage, but they are sexually immature and duller in color (the eyes, legs and genitalia are not fully developed). Depending on the species, within anywhere from a few minutes to a few days, the dun will molt a final time into the sexually mature adult (or imago).
Photo by: Peter Lesica on 4/11/21 in Missoula, MT