MOUTH - PARTS 



241 



of the maxillae which are large have small counterparts in the 

 labium, and vice versa. One of the commonest types is that 

 suited for piercing and sucking, that is, for making a hole in the 

 epidermis of a plant or animal and then drinking the sap or 



c 



— -r 



Fig. 176. — Diagram of the mouth-parts and adjacent region of the head of a 

 hemipterous insect. On the left are transverse sections (not all to the same 

 scale) at the levels shown by dotted hnes of the same lettering.— From Imms, 

 A General Textbook of Entomology, 3rd edition, i934- Methuen, London. 



cl clypeus : ec, ejection canal with salivary- duct ; /, labnim ; w, mandibles ; mx, maxilla ■ p pharynx 

 pd, pharN-ngeal duct ; r, labium ; sd, salivar>' duct ; sc, suction canal with phar>-ngeal duct. 



blood. In the aphis, which feeds on plant juices, the labium is 

 rolled to form an incomplete tube, in the hollow of which are 

 two pairs of stylets, which are the mandibles and maxillae 

 (Fig. 176). The two maxillae fit together in such a way as to make 

 two tubes, the smaller of which is used for conveying saliva 

 into the wound, and the larger for taking the food into the mouth. 

 The labium supports the stylets while they make a hole, often 

 deep into the plant tissues, in which process they are aided by 



