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mouthparts Modified paired appendages on the head segments of arthropods, used for feeding. A typical insect has a labium (lower lip), one pair each of mandibles and maxillae, and a labrum (upper lip), although in many the mouthparts are modified to form piercing stylets or a sucking proboscis. Crustaceans, centipedes, and millipedes have one pair of mandibles and two pairs of maxillae used for cutting and holding the food. Crustaceans also have several pairs of maxillipeds (see also maxillula). Arachnids have chelicerae and pedipalps.