Swarming effect help

[stevecullum]

I'm trying to create a swarm of Butterfly's and need some ideas to help add some realism. I've done some searches in this and other foums and came accross a convincing PFX setup which I can use as a base. However, when studying the behaviours of these Butterfly swarms I notice that there is banking going on as the instects change direction. Is there anyway to achieve this with the PFX system?

I was thinking of using animation path and doing it that way, but that effects the entire group and I would want some organic randomness thrown in.

Any suggestion are appreciated :)