hexapods

Hexapods are a subphylum of arthropods distinguished by having six legs. The vast majority belong to the class Insecta, though several related lineages are also included. Most hexapods have a body divided into three tagmata: head, thorax, and abdomen, and many possess wings during one life stage. They occupy a wide range of terrestrial and some freshwater habitats.

Anatomy and development: Hexapods typically have three pairs of legs attached to the thorax, a chitinous exoskeleton, and a segmented body. Insects breathe through a tracheal system with spiracles. Reproduction is primarily sexual, and development commonly includes metamorphosis: incomplete metamorphosis (egg, nymph, adult) or complete metamorphosis (egg, larva, pupa, adult).

Diversity and ecology: Hexapods are extremely diverse, with tens of thousands of described species of insects alone. Insect orders include Coleoptera (beetles), Lepidoptera (butterflies and moths), Diptera (flies), Hymenoptera (ants, bees, wasps), Orthoptera (grasshoppers, crickets), and Hemiptera (true bugs). Insects play essential ecological roles as pollinators, herbivores, predators, prey, and decomposers; many have complex life histories and social systems, especially in ants, bees, and termites. A minority of species are pests or disease vectors.

Evolution and discovery: Hexapods are among the earliest terrestrial arthropods, with fossil records dating from the Paleozoic. The emergence of flight and diverse metamorphoses are key drivers of their evolutionary success, enabling exploitation of new niches and rapid diversification.

Robotics: The term hexapod is also used for legged robots with six legs. Hexapod robots offer high stability on uneven terrain and are used in research and industry to study gait, manipulation, and search-and-rescue tasks. They typically employ tripod gaits that keep three legs on the ground at all times for balance.