Insects are neumerout invertebrate animals that belong in the PhylumArthropoda and Class Insecta. The class Insecta is divided into 2 subclasses:Apterygota, or wingless insects, and Pterygota, or winged insects. SubclassPterygota is futher divided on basis of metamorphosis. Insects that haveundergone incomplete metamorphosis are the Exopterygota. Insects that undergocomplete metamorphosis are the Endopterygota. Insects have an outer bilateral exoskeleton to which the muscles are attachedto and provides protection for internal organs. The body is divided into 3main parts which are the head, which include mouthparts, eyes, and antennae;thorax, which operate the jointed legs and /or wings; and abdomen, which hasorgans for digested food, reproducing, and getting rid of waste products. The major systems in insects are the circulatory, respiratory, nervous,muscular, digestive, and reproductive systems. In the circulatory system,blood is pumped by the heart in a tube to the aorta, the head, and to otherorgans then enters the ostia openings along the sides of the tube back to theheart. The respiratory systems carries O2 to cells and takes away CO2 fromcells through branching out to call cells of body. The nervous system consistsof a brain receiving information from eyes, antennae, and controls the wholebody and 2 nerve cords containing ganglia fused together to control activities

of the segment without the help of the brain. insect muscular system is madeup of a few thousand samll but string muscles allowing the insect to carry objectsheavier than it. The digestive system is basically a long tube where foodenters the mouth to the crop where it is stored, gizzard where it is grinded,stomach where it is digested, then the undigested parts and wastes are movedto the intestine, colon then released at the anus. And in the reproductivesystem, a new individual is produced sexually when the female eggs produced inthe ovaries united with male sperm produced in the testes. Both man and insect live almost everywhere, eat all kinds of food, and useall kinds of materials to build homes so they constantly live in conflict.Some insects seriously affect man's health and are parasitic on man and otheranimals. insects that feed on human or animal blood can carry disease in theirsalivary juices and spread the disease to other animals. Many insects irritateus without disturbing our health. Some bite and sting, and some people areallergic to them and some insects are injurious to our agricultural crops,food products, clothing, and wooden buildings. So far man has only partialsuccess in defending against insects. But some insects species are beneficialto man. The honey bee, for example, supplies us with honey and the silkwormsupplies us with silk. So bugs really aren't that bad.