From 
MSNBC News:
Many insects go back and forth between their nests and a food source multiple times. But if the route to the food is very similar to the route away from it, then the foragers might get confused and not know which way to go. Different insects have different ways of dealing with this problem. Bees use the sun as their compass. But ants use visual landmarks and let their stomachs guide their way, a new study finds. Wood ants were trained to walk in a straight line alongside a black wall to reach a sugar reward at the other end. In this way, the ants learned that the wall would be on their left side when walking towards the sugar but on their right side when walking away from it back home.
More here.