10-1 PHYSIOLOGY OP INSECTS. 



tally. Rudimental mandibles or mandibulcB incipientes, 

 are those which are perfectly without motion and appa- 

 rently without use ; they are small, scale-like processes 

 adhering to the skull, and are utterly incapable of gnawing 

 solid substances : they have this form in butterflies. Li- 

 near mandibles or mandibula lineares, are those which 

 are of uniform size and substance ; — which are perfectly 

 straight, parallel, and approximate ; they are always with- 

 out the horizontal motion, and utterly incapable of gnawing 

 solid substances : they have this form in many flies. Tu- 

 bulate mandibles or mandihul<B tubulatce, are those which 

 are hollow, and perforated at the extremity to admit the 

 passage of the blood of other insects, on which the insects 

 possessing such mandibles always feed : the mandibles 

 possess this form in the lance of some carnivorous beetles, 

 and in that of the ant-lion. Falciform mandibles or 7nan- 

 dibulce falciformes, are when they ai'e long and much 

 curved, in the shape of a sickle ; they move horizontally 

 with great ease, are hard and acute, and, when closed, 

 cross each other : insects possessing these mandibles bite 

 severely, and prey on other insects. Bifid mandibles or 

 mandibnlcB bifidce, are w^hen the extremity is terminated 

 by two distinct points of equal length and similar ap- 

 pearance, otherwise one of them would be called a tooth. 



^ _, Toothed mandibles or mandibula dentatcs^ 



ir (Z, are when the internal mandibles are beset 



\V < j^ with teeth : when this is the case, they are 

 4^]lJ?i hard and bony, have a rapid and powerful 

 Mandible. horizoutal motiou, and are capable of grind- 

 ing very hard substances. Setiform mandibles or mandi- 

 bulce setiformes, are when they are very slender, flexible, 

 thread-like, without horizontal motion, and often com- 

 pletely enclosed in a sheath, which sheath is generally 

 supposed to be the lower lip. 



