Insects

Insects that undergo three-stage metamorphosis lack a pupa, developing through a series of increasingly adult-like nymphal stages. Fossilized insects of enormous size have been found from the Paleozoic era, including giant dragonfly-like insects with wingspans of 55 to 70 cm (22 to 28 in). The most diverse insect groups appear to have coevolved with flowering plants. Humans regard many insects as pests, especially those that damage crops, and attempt to control them using insecticides and other techniques. Others are parasitic, and may act as vectors of diseases. Insect pollinators are essential to the reproduction of many flowering plants and so to their ecosystems. Many insects are ecologically beneficial as predators of pest insects, while a few provide direct economic benefit. Two species in particular are economically important and were domesticated many centuries ago: silkworms for silk and honey bees for honey. Insects are intentionally consumed as food in 80% of the world's nations, by people in roughly 3,000 ethnic groups. Human activities are having serious effects on insect biodiversity.