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MANUAL OF ZOOLOGY 



SECT. 



antennae vary a good deal in size and shape in different 

 Insects. The mandibles (Fig. 132, md.) lie at the sides of the 

 mouth, in front of which is a movable labrum or upper lip 

 (Ibr). Each mandible is a single solid piece, and is devoid 

 of a palp. The second maxillae (mx. 2) are united in their 

 basal portions to form a lower lip or labium. Jointed palps 

 (p.m.) are borne both by the first (maxillary palpi) and 

 by the second (labial palpi) pair of maxillae. All the jaws 



become variously modi- 

 fied in the different 

 orders in accordance 

 with differences in the 

 nature of the food. In- 

 sects which, like Cock- 

 roaches, Locusts, 

 Crickets and their allies 

 (Orthoptera) and Beetles 

 (Coleoptera), masticate 

 hard substances, have 

 the mandibles strong and 

 sharp and the maxillae 

 well developed, and all 

 the jaws are adapted to 



act as masticatory organs. Those, on the other hand, which, 

 like Cicadas, Bugs, Lice and Plant-lice (Hemiptera), live on 

 the juices of plants or animals, have the jaws in the form of 

 sharp stylets, enclosed in a sheath or proboscis, for piercing. 

 Intermediate conditions also occur. In the Hymenoptera 

 (Bees, Wasps, &c.), for example, the mouth parts are adapted 

 both for biting and for licking and sucking : the mandibles and 

 maxillae are sharp and lancet-like, and the middle part of the 

 labium is produced into a long median tongue, at the sides 

 of which are a pair of accessory tongues. In the Hemiptera 



FIG. 131. Cockroach (Periplaneta ameri. 

 cana). Lateral view of the head and its 

 appendages, cerv. one of the cervical 

 sclerites ; ey. eye ; gen. gena ; man. man- 

 dible ; max 1 , first pair of maxillae ; max' 2 . 

 second pair of maxillae (labium). 



