Entomology is the study of insects. As a subdiscipline of the biological sciences, it focuses on the life, history, morphology, physiology, genetics, reproduction, development and ecology of this most abundant and diverse taxonomic group of terrestrial organisms. The number of species of insects is estimated in the range of 5-10 million; the biology and ecology of most of these species are virtually unknown as only about 1 million species have been described by scientists.

Insects are most abundant and diverse in the tropics. They occupy nearly every conceivable terrestrial habitat and many freshwater ones. In contrast, the marine ecosystems possess only a few species. Due to their small size insects can inhabit a wide variety of microhabitats unavailable to larger animals. Many insects are phytophagous, feeding and living on various parts of plants such as seeds, flowers and stems. Some of these species, such as aphids, may transmit plant...