Yes, Dorian, I agree, but a person can go to a party and have a good time, meet people and even dance without being a "social butterfly". A "social butterfly" to me is someone who literally "flits" from party to party to be seen, who likes to "make the scene" and whose lifestyle is going to lots of social engagements. A "wallflower" is a person who doesn't like being social, is uncomfortable at a party or social gathering and was possibly forced to go. In that sense, they are opposites, when talking about parties. A loner or recluse are stronger terms than a wallflower. They give a more negative tone.