Phylum Arthropoda 517 



segmented bodies with but a single pair of legs on most segments. The 

 body consists only of the head and the many-segmented abdomen. The 

 head bears antennae, paired mandibles, and two pairs of maxillae. Res- 

 piration is by tracheae and excretion is by Malpighian tubules. The 

 sexes are separate, and the genital openings are near the posterior end. 

 The first body segment bears a pair of poison glands by which prey is 

 killed. In general, this poison is innocuous to human beings, but that 

 of some large tropical forms may cause painful wounds. Scutigera 

 forceps is the common house centipede and may often be seen running 

 rapidly with its fifteen pairs of legs. It feeds on flies and other small 

 arthropods and is completely harmless. 



