That sounds like a Particle thing. If you don’t have Trapcode’s Particular or Particle Illusion, you might want to click on Dan Ebberts head and scroll down to, “Building a 3D Particle Generator”. Download the project files.
You can supply your own particles, Dan uses tga’s and psds, but there is no reason you can’t use an animated butterfly comp as a particle. Most of Dan’s particles are 128×128.
Open the comp, Basic Explosion, or Explosion with Physics and delete all the particle layers (starflare.tga) and then Alt drag your butterfly comp onto the remaining particle layer, replacing it with you butterfly animation.
If you want to know how to do an animated butterfly, click on Aharon’s head and scroll down to his Flock of Birds tut. Just use butterfly parts.
So you can have your butterfly cruising around, then drop in your Butterfly explosion layer to get an explosion of Flutterbyes.