Insects are neumerout invertebrate animals that belong in the Phylum Arthropoda
and Class Insecta. The class Insecta is divided into 2 subclasses: Apterygota,
or wingless insects, and Pterygota, or winged insects. Subclass Pterygota is
futher divided on basis of metamorphosis. Insects that have undergone incomplete
metamorphosis are the Exopterygota. Insects that undergo complete metamorphosis
are the Endopterygota.

Insects have an outer bilateral exoskeleton to which the muscles are attached
to and provides protection for internal organs. The body is divided into 3 main
parts which are the head, which include mouthparts, eyes, and antennae; thorax,
which operate the jointed legs and /or wings; and abdomen, which has organs 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 other organs
then enters the ostia openings along the sides of the tube back to the heart.
The respiratory systems carries O2 to cells and takes away CO2 from cells
through branching out to call cells of body. The nervous system consists of a
brain receiving information from eyes, antennae, and controls the whole body and
2 nerve cords containing ganglia fused together to control activities of the
segment without the help of the brain. insect muscular system is made up of a
few thousand samll but string muscles allowing the insect to carry objects
heavier than it. The digestive system is basically a long tube where food enters
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 moved to the
intestine, colon then released at the anus. And in the reproductive system, a
new individual is produced sexually when the female eggs produced in the ovaries
united with male sperm produced in the testes.

Both man and insect live almost everywhere, eat all kinds of food, and use all
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 other animals.
insects that feed on human or animal blood can carry disease in their salivary
juices and spread the disease to other animals. Many insects irritate us without
disturbing our health. Some bite and sting, and some people are allergic to them
and some insects are injurious to our agricultural crops, food products,
clothing, and wooden buildings. So far man has only partial success in defending
against insects. But some insects species are beneficial to man. The honey bee,
for example, supplies us with honey and the silkworm supplies us with silk. So
bugs really aren\'t that bad.

Category: Science