Insects generally belong to the family of Insecta. They are invertebrates that are usually taxonomically. They are found plenty in number and of course the most widespread terrestrial taxon. And all these number count is strictly within the family of phylum Arthropoda. There are approximately 925,000 species, of which 5,000 dragonfly species, 2,000 praying mantis, 20,000 grasshopper, 170,000 butterfly and moth, 120,000 fly, 82,000 true bug, 360,000 beetle, and 110,000 bee, wasp and ant species. The size of an adult modern insect is approximately 0.139 mm to 555 millimetres. entomology is called as the study of insects, which is derived from the Greek word εντομος, which means "cut into sections" .Some of the other terrestrial arthropods are centipedes, millipedes, scorpions and spiders.
