Why do ants walk in a straight line ?

Ants walk in straight line is because ant leave a chemical trail for other ants to follow. They are following a trail laid out by another ant that will take them to food, water or their home. Ants leave this trail of pheromone or scent as they travel. After finding food they return to the nest following their own scent trail and communicate this fact to other ants who then follow then scent trail to the food. As more ants travel the trail scent gets more stronger easier to follow. And then random bumps are smoothed out making the trail straighter.