Beetles are the group of insects with the largest number of known species. They are classified in the order Coleoptera, which contains more described species than in any other order in the animal kingdom, constituting about 25% of all known life-forms. 40% of all described insect species are beetles, and new species are frequently discovered. Estimates put the total number of species, described and undescribed, at between 5 and 8 million. The largest family also belongs to this order the weevils, or snout beetles, Curculionidae. Beetles can be found in almost all habitats, but are not known to occur in the sea or in the polar regions. They interact with their ecosystems in several ways. They often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are prey of various animals including birds and mammals.