Insect Encyclopedia - Insects

Insects (昆蟲, Insect) are a class of animals belonging to the phylum Arthropoda, class Insecta, within the domain Eukaryota. They represent a massive group, accounting for two-thirds of all known animal species. Their bodies are divided into a head, thorax, and abdomen. The head features mouthparts and mandibles at the front, compound eyes on either side, simple eyes (ocelli) on the forehead, and a pair of antennae. The thorax has three pairs of legs underneath and two pairs of wings on the back. Respiration occurs through spiracles located along the sides of the abdomen. The class Insecta is divided into the subclass Apterygota, which have a single pair of mandibular appendages, and the subclass Pterygota, which have two pairs. Pterygota is further divided into the wingless subclass Apterygota and the winged subclass Pterygota. The winged subclass is then divided into the Palaeoptera, which can only move their wings up and down, and the Neoptera, which can move their wings backward as well. Neoptera is further divided into the Exopterygota and the Endopterygota, which undergo a pupal stage. Insects inhabit diverse ecosystems across the globe, excluding the oceans. Approximately 20,000 species are known in South Korea, with new species discovered annually.