(Not brilliant) Army Ant behaviour simulation.
The blue represents a square where there is at least 1 ant..up to a limit of about 20. 10 ants are created every time step from the nest (top left corner), and they can only move down or to the right until they hit food (yellow squares). When they hit food they turn back and go back to the nest. When an ant travels out from the nest to food they are more likely to go on squares where there are pheremones, and leave a single extra bit of pheremone on the squres, when they are carrying food, an ant drops 10 "pieces" of pheremone on the the squares on the way back to the nest.
When phermone levels on a squrae get above 100 they will start going shades of purple to show up pheremone concentrations. Pheremone evaporates from squares at a rate of e = 1/30.
This simulation is based upon Deneubourg et al's simualation as described in Bonabeau et als' book "Swarm Intelligence"
After leavnig this thing running for a few hours the following was left: