The sight of a single bull ant standing guard on the top of its nest will normally cause prudent humans to give the nest a wide berth. Why? Because most people know from experience, that if they are close enough to the nest to be perceived by a sentinel ant, a swarm of angry biting ants will quickly emerge from the nest and attack.
How does the sentinel ant alert other members of the ant colony that a threat is present?
Ants have complex societies with distinct caste systems. Workers and soldiers (sterile females), males and the queen all perform different tasks.
Pheromones play the central role in the organisation of ant societies. The ant colony itself has its own distinctive odour and ant castes are identified by differences in their secretions. Ants have a battery of exocrine glands to secrete pheromones as well as a battery of chemoreceptors to read and detect chemical messages. By blending and concentrating their chemical secretions ants are able to send messages and lay trails.
Although chemical communication is very important there are disadvantages, for instance rapid sequence signals are not possible because each chemical signal has to fade away before the next can be perceived. These problems are overcome by synergism - combining chemical communication with other methods. Ritualised, exaggerated movement such as head waving, vibrating antennae and mandible opening are used as signals. Tactile contact between individual ants is another means of communication. Ants also use acoustic communication. In its most simple form of sound creation ants can drum by rapping their bodies against the nest wall, however they may also use stridulation, which is the creation of sounds such as chirping, by rubbing specialist body parts together.
- Written by Nadia O'Carroll