Some visual differentiation would help, since currently everything is a white circle. The visual appearance could also be improved through motion behaviors that have more variability — right now everything seems to be moving around more like Pong balls (sliding linearly and then bouncing at 45 degrees) than actual organisms with ‘goals’ (see Craig Reynolds’s flocking applets or Valentino Braitenberg’s book, Vehicles. Here’s an applet that may be interesting …
http://www.markroland.com/processing/vehicle1/)