Ant (disambiguation)

Kingdom: Animalia Phylum: Arthropoda Subphylum: Hexapoda Class: Insecta Subclass: Pterygota Infraclass: Neoptera

Super Order: Endopterygota Order: Hymenoptera Suborder: Apocrita Superfamily: Vespoidea Family:Formicidae

Ants are social insects that belong to the same order as the wasps and bees. They are of particular interest because of their highly organized colonies or nests which sometimes consist of millions of individuals. Individuals are divided into workers, soldiers, drones and queens and colonies can occupy and use a wide area of land to support them. Ant colonies are sometimes described as super organisms because the colony appears to operate as a single entity.

Ants have colonized almost every landmass on Earth. They can constitute up to 15-25% of the total animal biomass. Up to a third (33%) of the terrestrial animal biomass has been estimated to be made up of ants and termites.

There are about 11,880 known ant species, most of which are tropical.

Termites, sometimes called white ants, though similar in social structure are not even closely related to ants. They comprise the more primitive order Isoptera and are more closely related to cockroaches. Velvet ants, although resembling large ants are wingless female wasps.

Evolution

Ants are classified as a family, Formicidae, belonging to the order Hymenoptera which also includes sawflies, bees and wasps. Ants are a lineage derived from within the vespoid wasps. Phylogenetic analysis indicates that ants evolved from other groups of wasps in the mid-Cretaceous period about 120 to 170 million years ago. After the rise of angiosperms about 100 million years ago, ant evolution also showed rapid change, and by about 60 million years ago ants had moved to ecological dominance. Several fossils from the Cretaceous are intermediate in form between wasps and ants, further confirming the wasp ancestry of ants. Like other Hymenoptera, the genetic system found in ants is Haplodiploidy.

In 1966 E. O. Wilson et al. obtained the first fossil remains of an ant (Sphecomyrma freyi) from the Cretaceous era. The specimen was trapped in amber from New Jersey that was more than eighty million years old. This species provides evidence of a link between modern ants and non-social wasps. Cretaceous ants shared a couple of wasp-like traits together with modern ant-like characteristics.

During the Cretaceous era, representatives of only a few species of primitive ants ranged widely on what was the super-continent Laurasia (the northern hemisphere). They were scarce in comparison to other insects (about only 1%). It was adaptive radiation which gave ants the dominance at the beginning of the Tertiary Period. Of the species extant in the Cretaceous and Eocene eras, only 1 of about 10 genera is now extinct. 56% of the genera represented on the Baltic amber fossils (early Oligocene), and 96% of the genera represented in the Dominican amber fossils (apparently early Miocene) still survive today.

Morphology

Ants are distinguished from other insects by the following traits: elbowed antennae; a strongly constricted second abdominal segment forming a distinct node-like petiole; the petiole can be formed by one or two "parts" or segments (only the second, or the second and third abdominal segments can form it). Ants have a wingless worker caste; the presence of a metapleural gland is also distinctive.

Ant bodies, like other insects, have an exoskeleton, meaning their bodies are externally covered in a protective casing, as opposed to the internal skeletal framework of humans and other vertebrates. Ants do not have lungs. Oxygen passes through tiny pores, the spiracles, in their exoskeleton - the same holes through which carbon dioxide leaves their body. Nor do they have a heart; a colorless blood, the hemolymph, runs from their head to rear and back again along a long tube. Their nervous system is much like a human spinal cord in that it is a continuous cord, the ventral nerve cord, from head to rear with branches into each extremity.

The three main divisions of the ant body are 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 thorax of the ant is where all six legs are attached. At the end of each leg is a sharp claw that helps ants climb and hang onto things. Most queens and male ants have wings, which they drop after the nuptial flight; however wingless queens (ergatoids) and males can occur.

The metasoma of the ant houses many of the important internal organs. Some species of ants have stingers used for subduing prey and defending their nests.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ant".