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From Wikipedia, the free encyclopaedia
Insects (Class Insecta), from Latin insectum (animal) "with a notched or divided body," The study of insects is called
entomology, from the Greek Insects are arthropods, having a hard exoskeleton, a three-part body (head, thorax, and
abdomen), three pairs of jointed legs, compound eyes, and two antennae. The head holds large compound eyes,
antenna (feelers), and the mouthpart. The legs (and wings, if applicable) are attached to the thorax. On most insects,
the abdomen is not an outstanding feature composed of 11 segments. On grasshoppers, there is a large round disc
on the first segment next to the thorax. It is called a tympanum and is the grasshopper's ear. And on each abdominal
segment, there is a small breathing hole called the thoracic spiracle. Insects are the most diverse group of animals
on the planet. There are approximately 2,200 species of praying mantis, 5,000 dragonfly, 20,000 grasshopper,
82,000 true bug, 120,000 fly, 110,000 bee, wasp ant and sawfly, 170,000 butterfly and moth, and 360,000 beetle
species described to date. Estimates of the total number of current species, including those not yet known to
science, range from two million to fifty million, with newer studies favouring a lower figure of about six to ten million.
With over a million described species-more than half of all known living organisms insects potentially represent over
90% of the differing life forms on the planet. They are most diverse at the equator and their diversity declines toward
the poles. Insects may be found in nearly all environments on the planet, although only a small number of species
occur in the oceans, a habitat dominated by another arthropod group, the crustaceans. Adult modern insects range
in size from a 0.139 mm (0.00547 in) fairyfly (Dicopomorpha echmepterygis) to a 56.7-centimetre (22.3 in) long
stick insect (Phobaeticus chani). The heaviest documented insect, of present species, was a Giant Weta of 70 g
(2½ oz), but other possible candidates include the Goliath beetles Goliathus goliatus, Goliathus regius and
Cerambycid beetles such as Titanus giganteus, though no one is certain which is truly the heaviest. The largest
insect was, in history, and is still believed to be the ancient dragonfly called Meganeura.