GENERAL ZOOLOGY 



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Fig. 15.16. Face view of a 

 small locust. Note the prom- 

 inent compound eyes and an- 

 tennae, and the shield-like 

 labrum coverina; the mouth 

 parts anteriorly. (Photo- 

 graph by Charles Walcott.) 



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are a pair of mandibles, or chewing jaws; a pair of maxillae, jointed, leaf-like 

 structures modified to aid in the manipulation of food; and a single lower lip, 

 the labium, which is derived during development by the fusion of a pair of 

 second maxillae. The mouth parts which are not segmental appendages are 

 the labrum, or upper lip, formed as a downgrowth from the anterior surface 

 of the head, and the hypopharynx, a median projection from the floor of the 

 mouth which acts more or less as a tongue. Possessing mandibles and other 

 mouth parts adapted for chewing, the locust is spoken of as a mandibulate 

 insect. As we shall see, in other insects the same fundamental mouth parts 

 may be modified for .sucking, for piercing and sucking, and for lapping; 

 however, the primitive insects are believed to have been mandibulate. 



Each of the three thoracic segments bears a pair of jointed appendages, 

 the legs. These are all similar in structure, but the posterior or metathoracic 

 legs are highly developed and specialized for leaping. At the distal end of 

 each leg, a small pad and a pair of hooks provide grasping organs by which 

 the insect obtains a firm hold upon vegetation. Two pairs of wings are 

 attached to the dorsolateral surfaces of the mesothoracic and metathoracic 



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