Insect anatomy

Insect anatomy

The morphology of insects enables the phenomenal success of this class of arthropods. The sheer quantity and diversity of its taxa are matched by a large variation of modifications in its body structure. The high rate of speciation, short generations and long lineage have caused insects to evolve in many ways resulting in very large variations in morphology. These modifications allow insects to occupy almost every ecological niche, utilise a staggering variety of food sources and possess diverse lifestyles. Insect body sizes range from 0.3 mm in the case of mymarid wasps, which parasitise insect eggs, to the 30 cms wingspan of the American owlet moth Thysania agrippina (family Noctuidae). Insects are by far the most successful group in the Arthropoda. They differ in significant ways from the other classes of Hexapoda, such as Protura, Collembola and others) who are now considered by some authorities to be more basal than insects. Insects (from Latin insectum, a calque of Greek ---? [entomon], "cut into sections") are a class of invertebrates within the arthropod phylum that have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. They are among the most

iverse groups of animals on the planet, including more than a million described species and representing more than half of all known living organisms.[2][3] The number of extant species is estimated at between six and ten million,[2][4][5] and potentially represent over 90% of the differing metazoan life forms on Earth.[6] Insects may be found in nearly all environments, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, crustaceans. The life cycles of insects vary (from one day to a few years), but most hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. The immature stages can differ from the adults in structure, habit and habitat, and can include a passive pupal stage in those groups that undergo complete metamorphosis. Insects that undergo incomplete metamorphosis lack a pupal stage and adults develop through a series of nymphal stages.[7] The higher level relationship of the hexapoda is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm (22–28 in). The most diverse insect groups appear to have coevolved with flowering plants.