The insects are the animal group with most diversity of species. Almost 750000 insect species are known, about 55% of the total already cataloged species of living beings (compare with mammals, with no more than 4000 known species). It is calculated however that the number of unknown species of insects may be over 2 million. The insect population on the planet is estimated to be more than 10 quintillion (1000000000000000000) individuals.
The great evolutionary success of insects is due to factors such as: small size and alimentary diversity, making possible the exploration of numerous different ecological niches; wings that provided more geographic spread; the tracheal respiration that gave them motor agility; high reproductive rates with production of great numbers of descendants.