A photo a day keeps the Doctor in play.
The butterflies are Eastern Tiger Swallowtails, if the Internet tells me true. Male Swallowtails engage in behavior called “puddling” in which they gather together on damp ground, a shoal or flat muddy bank, allegedly sucking up sodium ions and minerals dissolved in the water soaked into the mud, sand or gravel. I have seen a dozen or two Swallowtails do this, fluttering on the ground, seeming to strut past each other, along the B & O canal that parallels the Potomac River in Maryland, and here in Kentucky, in this case, on Floyds Fork. There are only three in the first picture because most of them flew away when I tried to sneak in for the close up. The Swallowtail in the second photo quietly endured the looming human bendling over with his iPhone. These butterfly moots look like a mating dance rather like what Swifts will do on a bank under a bridge, but evidently not. No ritual involved, just instinct to seek a particular nourishment.