WASPS 



195 



the pair of mandibles, the first pair of maxillae, and the second 

 pair of maxillae, of which the last-named are united to form 

 a single structure, the labium. The mandibles are the most 

 anterior of the jaws ; they are yellow in colour, and are hinged 

 on to the head a little way below the bottom of the compound 

 eyes, and form on the right and left sides movable boundaries 

 to the anterior part of the above-mentioned depression. Each 

 is actuated by powerful muscles, which cause it to bite against 

 its fellow in the middle line. The movement is thus from side 



FIG. 70. The mouth appendages of a wasp. A, ist maxilla : , cardo ; 

 s, stipes ; g, galea ; /, lacinia ; /, palp. B, labium. C, mandible, seen 

 from inner side. 



to side and not up and down, as is the case in our own jaws or 

 in those of any back-boned animal. The free extremities of 

 the mandibles are provided with strong horny black teeth, which 

 are used for cutting, scraping, or tearing, and behind the upper 

 of these, and separated from them by a groove, is a row of small 

 knobs resembling a coarse file, which is employed in crushing 

 substances from which juicy food can be extracted. Immedi- 

 ately behind the knobs is a number of fine hairs, which perhaps 

 function as a strainer and prevent solid matter from passing 

 into the mouth. About half-way along the inner, hollow face 

 is a strong transverse ridge ; the teeth of the other mandible 



