74 



ANIMAL BIOLOGY 



FIG. 123. MOUTH 

 PARTS OF BEETLE. 



of biting jaws (mandibles, ok\ (3) a pair of grasping 

 jaws (maxillae, A, >), and (4) a lower lip (labium, m, a, b). 



The grasping jaws bear two pairs of 

 jointed jaw fingers (maxillary palpi, 

 D, C\ and the lower lip bears a pair 

 of similar lip fingers (labial palpi, d). 

 The biting jaws move sideways ; they 

 usually have several pointed notches 

 which serve as teeth. Why should the 

 grasping jaws be beneath the chewing 

 jaws ? Why is it better for the lower 

 lip to have fingers than the upper lip ? 

 Why are the fingers (or palpi) 

 jointed ? (Watch a grasshopper 

 or beetle eating.) Why does an 

 insect need grasping jaws ? 



The chest, or thorax, consists 

 of three rings (Fig. 124) called 

 the front thorax (prothorax), 

 middle thorax (mesothorax) and 

 hind thorax (metathorax), or 

 first, second, and third rings. 



The first ring 

 bears the first 



pair of legs, the second ring bears the 

 second pair of legs and the upper or front 

 wings, and the third ring bears the third 

 pair of legs and the under or hind wings. 



The six feet of insects are characteristic of 

 them, since no other adult animals have that 

 number, the spider having eight, the craw- 

 fish and crabs having ten, the centipedes still more, while 

 the birds and beasts have less than six. Hence the insects 



FIG. 124. EXTERNAL PARTS 

 OF A BEETLE. 



FIG. 125. LEG 

 OF INSECT. 



