Hexapoda
Hexapoda is the arthropod group comprising insects and their wingless relatives. Its members have three pairs of legs attached to the thorax.
Arthropod: An invertebrate animal with a segmented body, jointed appendages, and an external skeleton. Hexapods form a major lineage within this broader animal group.
Arthropod appendage: A jointed body structure of an arthropod, including legs, antennae, and mouthparts. Hexapod legs and other specialized structures are modified appendages.
Arthropod evolution: The evolutionary history and diversification of arthropods, the largest animal phylum. Hexapod origins form one chapter in the wider history of arthropod diversification.
Pollination: The transfer of pollen to a plant's reproductive structures, enabling fertilization in seed plants. Many hexapods, especially insects, pollinate flowering plants.
Tagmosis: The evolutionary grouping of body segments into specialized regions, such as a head, thorax, and abdomen. Hexapod body regions arise through the specialization of serial segments.
Hox gene: A developmental regulatory gene that helps assign identities to body regions along an animal's head-to-tail axis. Hox genes help specify thoracic segments, where hexapod legs develop.
Pancrustacea: The evolutionary group comprising hexapods and crustaceans, supported by molecular and anatomical evidence. Evidence places hexapods within a broader lineage that also includes crustaceans.
Decomposition: The breakdown of dead organic matter into simpler substances by biological and physical processes. Soil-dwelling hexapods help fragment and process decaying material.
Thorax: The body region between the head and abdomen that bears the legs and, in many insects, wings. The three pairs of legs that characterize hexapods attach to this region.
Insect leg: A jointed appendage attached to an insect thoracic segment, typically built from several distinct parts. Its segment-by-segment attachment shows how hexapods bear three pairs of legs.