BUCCAL APPARATUS OP INSECTS. 



able to pierce the skin of animals or the vessels of plants, are 



the representatives of the 

 mandibles and the maxillae 

 extremely elongated. In those 

 Hemiptera which live at the 

 expense of other animals, the 

 proboscis is usually very firm, 

 and folds into a semicircle 

 under the head. Among those 

 which are nourished by suck- 

 ing vegetables, on the con- 

 trary, it is nearly always thin, 

 and is laid when in a state of 

 rest against the lower side of 

 the thorax, between the feet. 

 Its length is sometimes so 

 considerable, that it passes backwards behind the posterior ex- 

 tremity of the abdomen. 



616. Amongst the Flies, also, the proboscis, which is some- 

 times soft and retractile, sometimes horny and lengthened, repre- 

 sents the under lip, and often bears palpi at its base ; a longi- 

 tudinal channel occupies its upper side, which incloses the seta ; 



FIG. 320. BUCCAL APPARATUS OF AN 

 HEMIPTEROUS INSECT. 



FIG. 321. NEMESTRINA LONGIROSTRIS. 



whose number varies from two to six, their analogues amongst 

 the gnawing insects being the mandibles, the maxillae, and the 



