Some worker ants take the rubbish from the nest and put it outside in a special rubbish dump! Each colony of ants has its own smell to recognise intruders. Many ants such as the common Red species have a sting which they use to defend their nest. . Some birds put ants in their feathers because the ants squirt formic acid which gets rid of the parasites. If a worker ant has found a good source for food, it leaves a trail of scent so that the other ants in the colony can find the food.