Originally posted by Dead_Man_Inc:
like 2 ants crawling at each other's opposite direction, they will somehow touch or "kiss" each other when they met...
how come ar? communicate?
yes, it's communication through smell...
Ant communication is accomplished primarily through chemicals called pheromones. Because most ants spend their time in direct contact with the ground, these chemical messages are more developed than in other Hymenopterans. So for instance, when a forager finds food, she will leave a pheromone trail along the ground on her way home. In a short time other ants will follow this pheromone trail. Home is often located through the use of remembered landmarks and the position of the sun as detected with compound eyes and also by means of special sky polarization-detecting fibers within the eyes. Returning home, they reinforce this same trail which in turn attracts more ants until the food is exhausted, after which the trail is no longer reinforced and so slowly dissipates. This behavior helps ants adapt to changes in their environment. When an established path to a food source is blocked by a new obstacle, the foragers leave the path to explore new routes. If successful, the returning ant leaves a new trail marking the shortest route. Since each ant prefers to follow a path richer in pheromone rather than poorer, the resulting route is also the shortest available.
Ants make use of pheromones for other purposes as well. A crushed ant, for example, will emit an alarm pheromone which in high concentration sends nearby ants into an attack frenzy; and in lower concentration, merely attracts them. To confuse their enemies, several ant species even use what are termed propaganda pheromones.
Like other insects, ants smell with their antennae, which are long and thin. These are fairly mobile, having a distinct elbow joint after an elongated first segment; and since they come in pairs--rather like binocular vision or stereophonic sound equipment--they provide information about direction as well as intensity. Pheromones are also exchanged as compounds mixed with food and passed in trophallaxis, giving the ants information about one another's health and nutrition. Ants can also detect what task group (e.g. foraging or nest maintenance) to which other ants belong. Of special note, the queen produces a certain pheromone without which the workers would begin raising new queens.
Some ants also produce sounds by stridulation using the gaster segments and also using their mandibles. They may serve to communicate among colony members as well as in interactions with other species
http://en.wikipedia.org/wiki/Ant