class GnatSwarm extends Swarm
{
  GnatSwarm(Environment e)
  {
    super(e);
  }
  
  void update()
  {
    super.update();
    
    //remove dead gnats
    Particle p;
    Gnat gn;
    for(int i = 0; i < particles.size(); i++)
    {
      p = (Particle) particles.get(i);
      if (p instanceof Gnat)
      {
        gn = (Gnat) p;
        if (gn.isDead())
        {
          particles.remove(i);
          i--;
        }        
      }
    }
    
    //breed remaining gnats
    Particle p2;
    Gnat gn2;
    for(int i = 0; i < particles.size(); i++)
    {
      p = (Particle) particles.get(i);
      if (p instanceof Gnat)
      {
        gn = (Gnat) p;
        if (gn.isFertile())
        {
          p2 = (Particle) particles.get((int)random(particles.size()));
          if (p2 instanceof Gnat)
          {
            gn2 = (Gnat) p2;
            if (gn2.isFertile())
            {
              //println("before add particle " + particles.size());
              addParticle(gn.reproduce(gn2)); //we allow for asexual reproduction, but both parents must be fertile.
              //println("after add particle " + particles.size());
            }
          }                    
        }        
      }
    }
  }
  
}