insect summary

Learn about the classification of insects

Written and fact-checked by The Editors of Encyclopaedia Britannica

Below is the article summary. For the full article, see insect.

Body plan of a generalized insect. The body is usually divided into a head, thorax, and abdomen. The head bears appendages modified into mouthparts and antennae bearing sense organs. Mouthparts include the toothed mandibles and bladelike maxillae found behind the “upper lip,” or labrum. A second pair of maxillae, partly fused, form the “lower lip,” or labium. An adult usually has both simple eyes (ocelli) and more-complex faceted compound eyes, as well as a pair of wings on the thorax. The tarsal segment of the jointed leg often has claws with adhesive pads, enabling the insect to hold onto smooth surfaces. In some insects (including crickets and cockroaches), a pair of feelers (cerci) bearing sense organs are located at the rear of the abdomen. Tiny openings (spiracles) on the thorax and abdomen allow passage of oxygen to and release of carbon dioxide from internal air-filled tubules or tracheae. Sperm from the male is stored in the female's spermatheca until an egg released from the ovary passes through the oviduct. The female may have an ovipositor for depositing eggs.

insect, Any member of the class Insecta, the largest arthropod class, including nearly 1 million known species (about three-fourths of all animals) and an estimated 5–10 million undescribed species. Insect bodies have three segments: head, thorax (which bears three pairs of legs and usually two pairs of wings), and many-segmented abdomen. Many species undergo complete metamorphosis. There are two subclasses: Apterygota (primitive, wingless forms, including silverfish and bristletails) and Pterygota (more advanced, winged or secondarily wingless forms). The approximately 27 orders of Pterygota are generally classified by wing form: e.g., Coleoptera (beetles), Diptera (dipterans), Heteroptera (bugs). Insects are found in almost all terrestrial and freshwater and some marine habitats.

honeybee Summary

Honeybee, (tribe Apini), any of a small group of social bees that make honey. The tribe comprises a single genus —Apis—of which there are seven species. The term honeybee is commonly applied to a single species, Apis mellifera, the familiar and economically important western honeybee. Taxonomy See

mayfly Summary

Mayfly, (order Ephemeroptera), any member of a group of insects known for their extremely short adult life spans and emergence in large numbers in the summer months. Worldwide, more than 2,500 species of mayflies have been described, about 700 of them in the United States and Canada. Other common

caddisfly Summary

Caddisfly, (order Trichoptera), any of a group of mothlike insects that are attracted to lights at night and live near lakes or rivers. Because fish feed on the immature, aquatic stages and trout take flying adults, caddisflies are often used as models for the artificial flies used in fishing.

thrips Summary

Thrips, (order Thysanoptera), any of approximately 5,000 species of insects that are among the smallest of the winged insects and are abundant in the tropical and temperate regions of the world. Thrips are economically important since some species transmit plant viruses. Feeding by thrips may