This did appear to be some sort of disagreement. I've never seen two butterflies fighting;
maybe they got in somebody's leftover beer.
Oddly enough, they were away from the bunches, I guess they decided to "take it outside" 8^)
Some thought this might be a butterfly lovemaking ritual, which is a logical thought,
but the battle went on a long time and looked more like a barroom brawl.
The migratory generation of monarchs supposedly doesn't breed until spring, as the larvae would starve.