Ant Game

Along with the fighting game I am working on a tile based top down game where your character has to squash and use items to kill a certain number of ants, and you can lose by the ants reaching your counter where the food is ( there would be a food meter) I have the world created ( code as well) also i have the code for my character and his movement, I have hit a road block though for the code for my ants I want them to be motivated to move towards the food ( a certain tile) and there only to be a certain number of ants to be on the stage at a given time. so ants would be removed from the stage when they were killed or when they reach the food. any help would be appreciated.