Formicidae Ant

Ants are one of the most successful groups of insects in the animal kingdom . They are of particular interest because they are social insects and form highly organized colonies or nests which sometimes consist of millions of individuals. Colonies of invasive ant species will sometimes work together and form super-colonies, spanning a very wide area of land.

There are three main divisions to an ant's anatomy: the head, mesosoma and metasoma :

The head of an ant has many important parts. Ant eyes are compound eyes , similar to fly eyes: they have many smaller eyes attached together which enables them to see movement very well. Most ants have poor to mediocre eyesight; some are blind altogether. A few have exceptional vision though, such as Australia 's bulldog ant . Also attached to the head of an ant are two feelers . The feelers are special smelling organs that help ants communicate. Ants release pheromones (chemicals that have different smells) to communicate with each other and the feelers pick these smells as signals. The head also has two strong pinchers, the mandibles , which are used to carry food, to dig, and to defend. There is also a small pocket inside the mouth where ants can store food and give to others in need.

The life of an ant starts with an egg . Ants are holometabolous , and develop by complete metamorphosis , passing through larval and pupal stages before they become adults. A new worker spends the first few days of its adult life caring for the queen and young. After that it graduates to digging and other nest work, and then to foraging and defense of the nest. These changes are fairly abrupt and define what are called temporal castes. One theory of why this occurs is because foraging has a high death rate, so ants only participate in it when they are older and closer to death anyway. In a few ants there are also physical castes – workers come in a spectrum of sizes, called minor, median, and major workers, the latter beginning foraging sooner. Often the larger ants will have disproportionately larger heads, and so stronger mandibles. Such individuals are sometimes called "soldier" ants because their stronger mandibles make them more effective in fighting other creatures, although they are still in fact worker ants and their "duties" typically do not vary greatly from the minor or median workers. In a few species the median workers have disappeared, creating a sharp divide and clear physical difference between the minors and majors.

Ant communication is accomplished primarily through chemicals called pheromones. In a short time other ants will follow this pheromone trail. 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.

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.

Ants attack and defend themselves by biting and in many species, stinging, often injecting chemicals like formic acid.

Locomotion The more cooperative species of ants sometimes form chains to bridge gaps, whether that be over water, underground, or through spaces in arboreal paths. Termites , sometimes called "white ants," are in fact not closely related to ants, though they have a somewhat similar social structure.

Humans and ants
Ants are useful for clearing out insect pests and aerating the soil. On the other hand, they can become annoyances when they invade homes, yards, gardens and fields. Carpenter ants damage wood by hollowing it out for nesting. Nests may be destroyed by tracing the ants' trails back to the nest, then pouring boiling water into it to kill the queen. (Killing individual ants is less than effective due to the secretion of pheromones mentioned above). Many scales and homopteran species that are considered as horticultural pests are controlled by the use of grease rings on the trunks of the trees. These rings cut off the routes for ants and make the pest species vulnerable to parasites and predators.

Some species, called killer ants , have a tendency to attack much larger animals during foraging or in defending their nests. Human attacks are rare, but the stings and bites can be quite painful and in large enough numbers can be disabling.