Section 3

Subphyla Chelicerata and Myriapoda

• Members of the subphylum Chelicerata lack antennae and have pincerlike mouthparts called chelicerae.

• Arachnids include spiders, scorpions, mites, and ticks. Their bodies are divided into a cephalothorax and an abdomen, and they usually have six pairs of jointed appendages: one pair of chelicerae, one pair of pedipalps, and four pairs of walking legs.

• Spiders have eight simple eyes and chelicerae modified as fangs. Spiders produce silk threads that are used for several functions. Spiders are terrestrial; they respire by means of book lungs, tracheae, or both. Malpighian tubules function to excrete wastes while conserving water.

• Scorpions have large, pincerlike pedipalps and a stinger on the last segment of the abdomen.

• Mites and ticks have a completely fused cephalothorax and abdomen. Many species are parasitic, and some spread diseases that affect humans.

• Members of the subphylum Myriapoda have antennae, mandibles, and unbranched appendages.

• Millipedes have rounded bodies and two pairs of jointed legs on each body segment except the last two segments. Centipedes have flattened bodies and one pair of jointed legs on each body segment except the first segment and

Vocabulary arachnid (p. 731) pedipalp (p. 731)

spinneret (p. 732) book lung (p. 732)

trachea (p. 732) spiracle (p. 732)

Malpighian tubule (p. 732)

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