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How do insects differ from centipedes and millipedes?

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Illustration showing a variety of adult insects, each labeled with its common name and order, including walkingstick, earwig, stonefly, tree cricket, dragonfly, female scale, cat flea, thrips, sucking louse, thysanuran, ant, scarab beetle, stinkbug, mosquito, and cabbage butterfly, highlighting their diverse shapes and sizes. — insect An illustration of insect diversity.

Insects differ from centipedes and millipedes primarily in their body structure and classification within the phylum Arthropoda. While all three are arthropods with jointed legs and an exoskeleton, they belong to distinct groups with unique anatomical features.12

Key Differences

Body Regions: Insects (class Insecta) have bodies divided into three distinct regions: the head, a three-segmented thorax, and the abdomen. In contrast, centipedes (class Chilopoda) and millipedes (class Diplopoda) are myriapods, characterized by an elongated body with many trunk segments.134
Legs and Locomotion: Adult insects typically possess three pairs of legs attached to the thorax. Centipedes have one pair of legs per trunk segment, while millipedes are distinguished by diplosomites—fused double segments that each bear two pairs of legs.15643
Wings: A defining characteristic of many insects is the presence of wings, which are not segmental appendages but lateral folds of the integument. Centipedes and millipedes lack wings.1543
Head Appendages: Insects have one pair of antennae. Myriapods also possess antennae, but their mouthparts differ; for example, centipedes have specialized venomous claws behind the head, while millipedes have a single pair of maxillae fused into a plate.1643