Butterfly catchers

Butterfly Catchers is a derogatory term used to describe the more scientific-minded captains in the early Federation Starfleet.

The term was invented at a time when the direction of Starfleet wasn't yet established, and there was some strife between those captains who had been military veterans of the Earth-Romulan War, and those who were scientists. The war veterans felt that the scientists didn't have what it takes to command a starship, as they knew nothing of space combat.

The two groups were eventually able to reconcile. (Star Trek Novel: "Starfleet: Year One")