Hexapoda  

Eyes see in various wavelengths: birds
 

Eyes of some birds, insects, and fish see better than humans because they can detect ultraviolet and/or infrared light.

 
  "The eyes of some birds, insects, and fish respond to ultraviolet wavelengths. Other animals have a spectral response that includes red or near-infrared. This response is helpful in penetrating cloudy or murky conditions." (Courtesy of the Biomimicry Guild)
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Insects have a chitinous exoskeleton, a three-part body (head, thorax, and abdomen), three pairs of jointed legs, compound eyes, and two antennae. They are among the most diverse groups of animals on the planet, including more than a million described species and represent more than half of all known living organisms. There may be as many as 10 million living species. Insects may be found in nearly all environments, although only a small number of species occur in the oceans, a habitat dominated by different type of arthropod, the crustacea. The life cycles of insects vary but most hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of moults. 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. 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. Insects typically move about by walking, flying or occasionally swimming. As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles. Insects are the only invertebrates to have evolved flight. Many insects spend at least part of their life underwater, with larval adaptations that include gills and some adult insects are aquatic and have adaptations for swimming. Some species, like water striders, are capable of walking on the surface of water. Insects are mostly solitary, but some insects, such as certain bees, ants, and termites are social and live in large, well-organized colonies. Some insects, like earwigs, show maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over distances of many kilometers. Other species communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males. Lampyridae in the beetle order Coleoptera communicate with light. Some insects damage crops by feeding on sap, leaves or fruits, a few bite humans and livestock, alive and dead, to feed on blood and some are capable of transmitting diseases to humans, pets and livestock. Without insects to pollinate flowers, many crop plants would not be able to reproduce. Many other insects are considered ecologically beneficial as predators and a few provide direct economic benefit. Silkworms and bees have been used extensively by humans for the production of silk and honey, respectively.

Sensilla detect strain and load changes: insects
 

The exoskeleton of insects detects strain and load via sensilla organs.

 
  "In their rigid state exoskeletons are stiff laminated composite structures made of chitin fibres embedded in a highly crossed matrix. The exoskeleton acts as a detector of displacement, strain or load via special organs called sensilla, which are partly intergraded into local sections of exoskeleton. These organs amplify the information for the main detector organ, which is connected to the nerve stem. The local information obtained is used to modify the exoskeleton by changing thickness, stiffness and fibre orientation depending on the situation." (The University of Bath 2008)
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Common and diverse Sexual Dimorphism; can be pronounced; females usually larger than males but the reverse occurs; Sexual Dimorphism also in color and in shape and size of body segments, genitalia and appendages; male appendages often specialized for detecting pheromones, sexual signals, sperm transport or

grasping females; females often with specialized ovipositors.