Insects make up approximately 80 percent of the total number of animals on Earth.
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Insects have jointed bodies divided into three segments: the head, thorax and abdomen.
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Fossil records show that insects existed 390 million years ago. Some of the earliest insects, such as cockroaches, have changed very little.
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Instead of internal skeletons, insects have exoskeletons -- tough outer coverings made up of several layers. The most rigid of these layers is composed of chitin, a horny, waterproof substance.
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The simple eyes, or ocelli, are located on the head between the compound eyes. The ocelli aren't used for vision, but to detect changes in the intensity of light.
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Although insects breathe air, they don't have lungs. Instead, a system of branching air tubes, or tracheae, reaches all parts of the body. Air enters through openings called spiracles.
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Complete, or indirect, metamorphosis follows this developmental pattern: egg, larva, pupa, adult.
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Less than 2 percent of all insect species are harmful; but among them, they can cause major crop damage and spread serious diseases.
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A general rule of thumb is not to eat any brightly colored insect since it's nature's way of warning predators that this insect is poisonous.
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There are 1,417 species of edible insects and nearly 3,000 ethnic groups that currently practice entomophagy around the world.
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