During the Cretaceous period, a few species of primitive ants ranged widely on the Laurasian super-continent (the northern hemisphere). They were scarce in comparison to the populations of other insects, representing only approximately 1% of the entire insect population. Ants became dominant after adaptive radiation at the beginning of the Paleogene period. By the Oligocene and Miocene ants had come to represent 20–40% of all insects found in major fossil deposits. Of the species that lived in the Eocene epoch, approximately one in ten genera survive to the present. Genera surviving today comprise 56% of the genera in Baltic amber fossils (early Oligocene), and 92% of the genera in Dominican amber fossils (apparently early Miocene). Termites, although sometimes called white ants, are not ants. They belong to the order Isoptera. Termites are more closely related to cockroaches and mantids. Termites are eusocial, but differ greatly in the genetics of reproduction. That their social structure is similar to that of ants, is attributed to convergent evolution.Velvet ants look like large ants, but are wingless female wasps. Ants are found on all continents except Antarctica, and only a few large islands such as Greenland, Iceland, parts of Polynesia and the Hawaiian Islands lack native ant species.Ants occupy a wide range of ecological niches, and are able to exploit a wide range of food resources either as direct or indirect herbivores, predators, and scavengers. Most species are omnivorous generalists, but a few are specialist feeders. Their ecological dominance may be measured by their biomass and estimates in different environments suggest that they contribute 15–20% (on average and nearly 25% in the tropics) of the total terrestrial animal biomass, which exceeds that of the vertebrates. Ants range in size from 0.75 to 52 millimetres (0.030–2.0 in), the largest species being the fossil Titanomyrma giganteum, the queen of which was 6 centimetres (2.4 in) long with a wingspan of 15 centimetres (5.9 in).Ants vary in colour; most ants are red or black, but a few species are green and some tropical species have a metallic lustre. More than 12,000 species are currently known (with upper estimates of the potential existence of about 22,000) (see the article List of ant genera), with the greatest diversity in the tropics. Taxonomic studies continue to resolve the classification and systematics of ants. Online databases of ant species, including AntBase and the Hymenoptera Name Server, help to keep track of the known and newly described species.The relative ease with which ants may be sampled and studied in ecosystems has made them useful as indicator species in biodiversity studies.
Posted on: Sun, 10 Nov 2013 13:10:10 +0000
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