What is the importance of smell to an ant?

Ants dont smell in the conventional sense of the Word. Their antennae are chemical receptors that can detect changes in their surroundings from pheromones that other ants excrete. This is usually from their feet so that when they walk about they leave a trail others can follow on. If there is something interesting at the end of the trail it is used more often so the trail has more aroma so more ants follow it. this follows the runaway principle where one route is embraced and other less well used routes are forgotten about in time. However it the trail is lost ants will often start following others near them. This can often lead to circles of ants following each other getting smaller and smaller until they all starve to death.