Kelly shared several photos of some mayfly beauties she found on her porch. Although these two look markedly different, we believe them to be the same species. The top mayfly, with the kind of milky-white wings, is in its first winged stage, while the bottom mayfly is in its second (and final) winged stage.
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). The mature adults lead ephemeral lives, normally living only a day or two, and with only vestigial mouthparts, they do not eat. View a succinct animation of the life cycle, created by the Watershed Education Network, here.
Our best guess for an ID: Comb-mouthed Minnow Mayflies (in the family Ameletidae, genus Ameletus). Let us know what you think!
Size: Body length around 10 mm
Photos by: Kelly Dix on 4/25/22 in Lolo, MT