Ants use special nerve cells associated with tiny hairs on their antennae to smell odors. The kind of ants you see in your kitchen probably have a few thousand of these “smell cells,” and the cells are tuned to different classes of odors.
Ants seem to be able to smell most of the substances humans can smell. An ant worker foraging for food might find a tasty morsel by chance. As it returns to the nest, the ant will leave behind a chemical trail for co-workers to follow back to the food source. Within minutes you might find a line of ants leading to your bit of cheese.
The brain that controls all this has a volume of about one one-thousandth of a cubic millimeter, and may contain somewhere between 20 thousand and 100 thousand nerve cells. Compare that with the human brain. Our brains contain roughly ten to the twelfth nerve cells – that’s a one with twelve zeros at the end.