4 GENERAL ZOOLOGY 



short feeler-like organs called palpi. The hard mandibles 

 grind the food, which is held and passed in to them by the 

 other mouth parts. 



The Thorax. The first somite of the thorax, called the 

 prothorax (Fig. 2), bears the first pair of legs. It is free 

 from the rest of the thorax. The dorsal surface (Lat. dor- 

 sum, " back ") is thickened and raised into a ridge, the sides 

 (lateral surfaces) are also thickened, and the whole forms 

 a protective shield or collar. The second somite, the meso- 

 thorax (Fig. 2), bears the second pair of legs; to the third, 

 or metathorax, the last pair of legs is attached. Each leg is 

 composed of a number of divisions, of which the principal 

 are the thick femur (Figs. 2, 3) and the spiny tibia (Fig. 3). 

 Each leg ends in a series of three small joints, forming the 

 tarsus, or foot, the last division of which bears two claws, 

 with a pad, the pulvillus, between them. 



Of the two pairs of wings (Fig. 2), the first is attached to 

 the surface of the mesothorax, the second to the metathorax. 

 The anterior pair is somewhat hardened, forming protective 

 covers for the more delicate posterior wings, which are 

 folded like a fan beneath them. The latter only are used 

 in flight. The wings are simple extensions of the body wall, 

 and not jointed appendages like the legs. On the sides, just 

 beneath the posterior edge of the collar on the prothorax, is 

 a pair of breathing openings, or spiracles (not shown in the 

 figure). Two spiracles are placed just above the junction of 

 the second pair of legs (Fig. 2), and the abdomen bears eight 

 pairs along the sides. 



The Abdomen. The first abdominal somite is much larger 

 than the others, though it does not form a complete ring, 

 owing to the space occupied by the cavities for the attach- 

 ment of the hind legs. Each side of this somite bears an 

 oval spot consisting of a thin skin stretched across a small 

 cavity and connected with a nerve, the whole forming an 



