With the exception of a heart and an aorta, there are few blood vessels insect blood simply flows around inside the body cavity. The internal anatomy of insects is characterized by an open circulatory system, a multitude of breathing tubes, and a three-chambered digestive system. The abdomen functions in digestion and reproduction. The legs may be adapted for running, grasping, digging, or swimming. The thorax provides structural support for the legs (three pairs) and, if present, for one or two pairs of wings. Insect mouthparts have evolved for chewing (beetles, caterpillars), piercing-sucking (aphids, bugs), sponging (flies), siphoning (moths), rasping-sucking (thrips), cutting-sponging (biting flies), and chewing-lapping (wasps). The head functions mainly for food and sensory intake and information processing. Insects have three body regions: head, thorax, and abdomen. Sense organs may be located almost anywhere on the insect body, not just on the head. The exoskeleton also has many sense organs for detecting light, pressure, sound, temperature, wind, and odor. This multi-layered exoskeleton protects the insect from the environment and natural enemies. Their muscles and organs are on the inside. Insects and closely related organisms have a lightweight, but strong exterior skeleton (exoskeleton) or integument. The more we know about their biology and behavior, including their natural enemies, the more likely we will be able to manage them effectively. The adage 'know your enemy' is especially appropriate when it comes to insect pests. In the context of agriculture, an insect is a pest if its presence or damage results in an economically important loss. In reality, less than one percent of insect species are pests, and only a few hundred of these are consistently a problem. At the same time, insects are major pests of humans and domesticated animals because they destroy crops and vector diseases. Indirectly, they are important as pollinators of crops, natural enemies of pests, scavengers, and food for other creatures. Insects are directly beneficial to humans by producing honey, silk, wax, and other products. This makes them an especially formidable pest of crops, able to adapt to new plant varieties as they are developed or rapidly becoming resistant to insecticides. Insect populations also possess considerable genetic diversity and a great potential for adaptation to different or changing environments. In addition, insects can produce large numbers of offspring relatively quickly. Because they are small they require only small amounts of food and can exist in very small niches or spaces. Their small size and ability to fly permits escape from enemies and dispersal to new environments.

It is believed that insects are so successful because they have a protective shell or exoskeleton, they are small, and they can fly. Insects possess an amazing diversity in size, form, and behavior. If they are not physically equipped to live in a stressful environment, insects have adopted behaviors to avoid such stresses. The only place where insects are not commonly found is the oceans. Insects are extraordinarily adaptable creatures, having evolved to live successfully in most environments on earth, including deserts and the Antarctic. They also play a major role in the breakdown of plant and animal material and constitute a major food source for many other animals. Of all creatures on earth, insects are the main consumers of plants. About one million species have been described, and there may be as many as ten times that many yet to be identified.

Millions may exist in a single acre of land. Insects are the dominant life-form on earth. Insect Classification and Identification.Insect Growth and Development (Metamorphosis).This segment is comprised of several paragraphs of general insect information and five subsections: For the reader who is unfamiliar with the biology or ecology of insects, this primer will provide needed background information.

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