308 



THE ANIMAL KINGDOM 



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Figure 16.18. Head and mouth parts of the cockroach (mouth parts viewed from 

 behind. (Combined from Comstock and Parker and Haswell.) 



omnivorous habit. Each mandible is a single segment with sharp cutting 

 and grinding teeth along the medial edge. Each maxilla has seven seg- 

 ments ol which the last five lorm a tactile palp. The second segment is 

 large and bears two processes. The labium is similarly constructed, ex- 

 cept that the two basal segments are fused and the palps are four- 

 jointed. The processes on maxillae and labium, together with the 

 labrum, manipulate and hold food for the mandibles. 



A short neck joins the head to the thorax. The latter is formed of 

 three fused segments, the prothorax, mesothorax and metathorax. The 

 back or notum of the prothorax is expanded as a shield partially cov- 

 ering the head and mesothorax. The nota of the other two segments 

 are covered by the wings. On the ventral side oblique lateral plates or 

 pleura join the three nota to the sterna, three triangular plates in the 

 midline. Each sternum bears a pair of legs, while the nota and pleura 

 of the last two segments articulate with the wings. 



Each leg (Fig. 16.17) is composed of a large flattened coxa, small 

 trochanter, long, stout femur, long, slender tibia, and five small seg- 

 ments collectively called the tarsus. Many of these segments are beset 

 with spines. Each tarsal segment ends ventrally in a small adhesive 

 pad. The last, called the pulvillus, is the largest and is flanked by a 

 pair of tarsal claws. Joints between coxae and body permit only a 

 slight movement, and the trochanters are fused immovably onto the 

 femurs. Most of the locomotion is derived from movements between 

 coxae and trochanters, and between femurs and tibias. The claws and 

 pulvilli provide for a grip on any kind of surface, and the several small 



