An ant script saved from https://github.com/jywarren/antfarm

ant.js

// set basic attributes here;
// "this" means this ant you're editing now
this.speed = 1;
this.color = 'red';
this.height = 40;
this.width = 40;

// runs every frame:
onRun = function () {

  this.direction += Math.random()*10-5; // vary direction slightly, randomly, in degrees
  field.trail(this.x,this.y,'blue',100); // leave a trail at x, y, color, amount
  // every 30 frames:
  if (field.time % 30 == 0) {
    // make a new ant
    var ant = field.populate(AntFarm.Ant, 1)[0];
    ant.x = this.x;
    ant.y = this.y;
    ant.color = "blue";
    ant.speed = 3;
    ant.onRun = function () {

      if (this.age < 300) {
        this.direction += Math.random()*10-5;
        field.trail(this.x, this.y, 'blue', 50); // x, y, rgb, amount
      } else {
        this.speed = 0;
        this.color = "grey";
      }

    }
  }
}

onBump = function () {

  // change direction by 90 degrees:
  this.direction += 90;

}