Insects

Insects are a class of arthropods and comprise the largest and most diverse group of animals on Earth. They have a chitinous exoskeleton, a body divided into three main segments (head, thorax, abdomen), one pair of antennae, and typically six legs. Many also bear one or two pairs of wings at some life stage. Insects occupy nearly every habitat, from deserts to forests, grasslands, mountains, and freshwater environments.

Most insects undergo metamorphosis, which comes in two main forms. Incomplete metamorphosis (hemimetabolism) includes egg, nymph, and adult stages; nymphs resemble smaller versions of adults and molt as they grow. Complete metamorphosis (holometabolism) includes egg, larva, pupa, and adult, with immature stages often looking very different from the adults (for example caterpillars and butterflies or beetle larvae and adults).

Anatomically, insects breathe through a tracheal system connected to spiracles on the body surface. They typically have compound eyes and mouthparts adapted to diverse diets, including chewing, sucking, or lapping. The forewings of beetles are hardened into elytra that protect the hind wings and abdomen.

Ecologically, insects fulfill essential roles. They pollinate many crop plants and wildflowers, help decompose organic matter, and form a major part of food webs as herbivores, predators, parasitoids, and prey. Some species are pests or disease vectors, while others provide benefits as pollinators, biocontrol agents, or model organisms in science (for example Drosophila melanogaster).

Threats to insects include habitat loss, pesticides, pollution, and climate change, which can reduce diversity and disrupt ecosystems. Conservation and sustainable management aim to balance human needs with the preservation of insect biodiversity.