(from  insectum) are pancrustacean hexapod invertebrates of the class Insecta.

They are the largest group within the arthropod phylum. have a chitinous exoskeleton, a three-part (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae.

are the most diverse group of ; they include more than a million described  and represent more than half of all known living organisms.

The total of extant  is estimated at between six and ten million; potentially over 90% of the life forms on are .

may be found in nearly all environments, although only a small of reside in the oceans, which are dominated by another arthropod group, crustaceans, which recent has indicated are nested within.


Nearly all hatch from .

growth is constrained by the inelastic exoskeleton and development involves a of molts.

The immature stages often differ from the adults in structure, habit and , and can include a passive pupal stage in those groups that undergo four-stage metamorphosis.

that undergo three-stage metamorphosis lack a pupal stage and adults develop through a of nymphal stages.

The higher level relationship of the  is unclear. Fossilized of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm (22 to 28 in). The most diverse groups appear to have coevolved with  .

Adult typically move about by walking, flying, or sometimes swimming.

As it allows for rapid yet stable movement, many adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles, composed of the front and rear on one side with the middle on the other side.

are the only invertebrates to have evolved flight, and all flying derive from one common ancestor.

Many spend at least part of their lives under , with larval adaptations that include gills, and some adult are aquatic and have adaptations for swimming.

Some , such as  striders, are capable of walking on the surface of .

are mostly solitary, but some, such as certain bees, ants and termites, are social and live in large, well-organized colonies.

Some , such as earwigs, show maternal care, guarding their and young.

can communicate with each other in a variety of ways.

Male moths can sense the pheromones of female moths over great distances.

Other communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males.

Lampyrid beetles communicate with light.

Humans regard certain as pests, and attempt to control them using insecticides, and a host of other .

Some damage crops by feeding on sap, leaves, fruits, or .

Some are parasitic, and may vector diseases. Some perform complex roles; blow-flies, for example, help consume carrion but also spread diseases.

 pollinators are essential to the life cycle of many on which most organisms, including humans, are at least partly dependent; without them, the terrestrial portion of the biosphere would be devastated.

Many are considered ecologically beneficial as predators and a few provide direct benefit.

Silkworms  silk and bees   and both have been domesticated by humans.

are consumed as in 80% of the world's nations, by in roughly 3000 ethnic groups.

activities also have effects on  .

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