Red Admiral (Admirable) or Vanessa atalanta butterfly

There was a group (flock?) of  these butterflies around a dead tree at the edge of the parking lot.  Better images on line.  They are apparently not uncommon along the east coast, breeding twice in the south once in the north and often more late in the year.  That might have been the behavior we were seeing.

They also apparently feed on the sap of trees, so they may have been feeding even though the tree looked at least dormant if not dead.

So a strategy of breeding late in the year before migration south, and being able to feed on trees.

( and a group of butterflies can be called a swarm but more technically is a kaleidoscope, will cousin Ted know that one?)

Struggling through Nabokov's novel Pale Fire, noted a reference to this butterfly(he studied butterflies as a hobby).  It may have originally been the Red Admirable, later corrupted to Admiral.  Like Admirable better.