Vladimir Nabokov, Butterfly Illustrator (2016)

They move their wings quite a bit relative to each other. Usually they do hold them a bit further back, and she explained in her blog entry. But they are capable of moving them far forward when they want. Sometimes the patterns are strikingly different when they do so.

It is most noticeable in a swarm, where little flashes of different color wind up catching your eye against the background of the more general form. Almost like the flashes of silver you sometimes see in an active school of sardines or the like. And who knows? Maybe even for the same reason, as a response to similar environmental pressures!