438 EXTERNAL ANATOMY OF INSECTS. 



many have no other tools to aid them in their various 

 labours and mechanical arts : to some they supply the 

 place of trowels, spades, and pick-axes ; to others that of 

 saws, scissors, and knives — with many other uses that 

 might be named. In fact, with the insects of this intire 

 Order mastication seems merely a secondary, if it is at 

 any time their use. Still comprehending in one view all 

 the mandibulate Orders, though some use their mandi- 

 bles especially for purposes connected with their economy, 

 yet their most general and primary use is the division, 

 laceration, and mastication of their food ; and this more 

 exclusively than can be affirmed of the under-jaws (max- 

 illa:). This will appear evident to you, when you consi- 

 der that insects in their larva state, in which universally 

 their primary business is feeding, with very few excep- 

 tions use the organs in question for the purpose of masti- 

 cation, even in tribes, as the Lepidoptera, that have only 

 rudiments of them in their perfect state — while the ?nax- 

 illde ordinarily are altogether unapt for such use. The 

 exceptions I have just alluded to are chiefly confined to 

 the instance of suctorious mandibles; or those which, 

 being furnished at the end with an orifice, the animal in- 

 serting them into its prey, imbibes their juices through 

 it. This is the case with the larvae of some Dytisci, He- 

 mefobius, and Myrmeleon* ; and spiders have a similar 

 opening in the claw of their mandibles, which is sup- 

 posed to instil venom into their prey b . 



Under this head I must not pass without notice an 

 appendage of the mandibles, to be found in some of the 



a In the Myrmeleon, or ant-lion, the suction is promoted by the 

 action of a piston, that pumps up the juices. Reaum. vi. 3G9. 

 h De Geer iv. 380'—. t. xv./. 10. See above, p. 121. 



