Best guess; submerged and attached to vegetation
this dude was absolutely cruising along the ground, so it was hard to get a clear picture. it looks like the four-spotted carrion beetle doesn't appear in the US (yet?), but i couldn't find anything that looks as close! please feel free to fix this observation as necessary, i have no idea what i'm looking at
Found indoors at a home in Monroe County NY in late November. Approximately 6 inches long tail to nose.
60cm roughly- rescued from field while parking cars for fair
Dark brown body & eyes, about 11 mm size. Middle tail doesn't seem particularly short (that would be a characteristic of Lepto), but the dark body and rounded leading edge of the back wing suggests Leptophlebia rather than E. subvaria, which is another large mayfly appearing here this time of year (subvaria has more of a pointed or sharply projecting hind wing edge).