Fun Facts Dogs have about 100 million smell cells per nostril. Many creatures communicate by smell, they produce chemicals called pheromones which can signal danger, fear, anger, where food is, or where a mate is. A skunk's spray, for example, definitely signals warning. Insects especially rely on this kind of communication. The huge column of ants leading from the anthill to your picnic is following a pheromone trail laid down by the first ant to find your food.
Humans use pheromones to control insect pests.
Mosquitoes stay away, not because you stink, but because your smell seems dangerous and many harmful insect pests are being tricked into traps which have attractive pheromones. Scientists are not yet sure if humans use pheromones to communicate. However, some moms can almost always tell which T-shirt belongs to their child when jumbled with other kids' shirts. They can even tell brothers' or sisters' shirts apart with just a sniff. For example, you know an apple because is it roundish, shiny, red or green and has a stem on top.