What Is The Definition Of An Insect?

Insects collected by school boys everywhere are taxonomically referred to as the class Insecta. Insect is the most diverse group of animals on the earth, and are divided into 14 subcategories:
Hymenoptera: Ants, bees and wasps
Diptera: Flies
Neuroptera: Lacewings and antlions
Hemiptera: True bugs
Mantodea: Mantids
Phsmida: Walking Sticks
Ephemeroptera: Mayflies
Lepidoptera: Butterflies and moths
Coleopera: Beetles
Homoptera: Cicada, Hoppers and Aphids
Blattaria: Cockroaches
Orthoptera: Grasshoppers and Crickets
Odonata: Dragonflies and Damselflies
Arthropoda: Those that have segmented feet
Some non insects such as spiders, centipedes and scorpions are at times mistakenly classified as insects.

True insects of the class Insecta have exposed mouthpieces and eleven abdomen sections and are known as ectognatha. Insects have very sensitive organs of perception. Some species such as bees and ants survive in forms of advanced colonies which are thought of as the most sophisticated societies. Insects first dawned in this world 350 million years ago, when they make a surprise entrance. Their bodies are divided into a head, a thorax, and an abdomen. The head supports a pair of sensory antennae, a pair of compound eyes and mouth parts, and many develop wings as adults. Many are useful to man, and in some parts of the world constitute food.