The order Coleoptera includes more species than any other order, constituting almost 25% of all known life-forms. About 40% of all described insect species are beetles (about 400,000 species) and new species are discovered frequently. Some estimates indicate the total number of species, described and undescribed, as high as 100 million, however; a figure of 1 million is more widely accepted. The largest taxonomic family, the Curculionidae (the weevils or snout beetles), also belongs to this order.
The diversity of beetles is wide ranging. They are found in all major habitats, except marine and polar regions. They have many classes of ecological effects; there are particular species that are adapted to practically every kind of diet. Some are non-specialist detritus feeders, breaking down animal and plant debris. Some feed on particular kinds of carrion such as flesh or hide while others feed on wastes such as dung. Some feed on fungi and others feed on particular species of plants. Some feed on a wide range of plants; some are generalist pollen, flower and fruit eaters. Some are predatory, usually on other invertebrates; some are parasites or parasitoids. Many of the predatory species are important controls of agricultural pests. For example, ladybugs consume aphids, scale insects, thrips, and other plant-sucking insects that damage crops.
Conversely beetles are prey of various invertebrates and vertebrates including insects, fish, reptiles, birds and mammals. The Coleoptera are not generally serious pests, but they include agricultural and industrial pests.