Entomology is the study of insects. It is a major branch of animal zoology. Insects are one of the most successful and diverse groups of living organisms in the world today. Approximately 1.5 million species of insects have been identified by scientists as of the end of the twentieth century. However, it is estimated there may be as many as twice that number on Earth. The number of insect species is greater than the number of all other species of organisms combined. It is estimated that there are about 200 million insects for every living human. Insects are members of the kingdom Animalia, the phylum Arthropoda, and the class Insecta. Insects share the major group Arthropoda with creatures such as crabs, lobsters, shrimp, spiders, scorpions, ticks, mites, centipedes, and millipedes. Common insects include ants, butterflies, bees, cockroaches, beetles, flies, grasshoppers, mosquitoes, dragonflies, moths, wasps, and termites.

Insects have a tough...