386 THE PHILOSOPHY 



marches from branch to branch, and, when difpofed for food, at- 

 tacks and devours the firfl caterpillar that comes in its way. 



The pucerons, vine-fretters, or plant-lice, are very injurious to 

 trees and vegetables of almoft every kind. Their fpecies are fo nu- 

 merous, and all of them are endowed with fuch a wonderful ferti- 

 lity, that we fhould expedl to fee the leaves, the branches, and the 

 ftems of every plant totally covered with them. But this aftonifh.- 

 ing fecundity, and the devaftation thefe fmall infeds would una- 

 voidably produce among the vegetable tribes, is checked by num- 

 berlefs enemies. Myriads of Infeds of different clafTes, of different 

 genera, and of different fpecies, feem to be produced for no other 

 purpofe but to devour the pucerons. Some of thefe infefts are fo 

 voracious, that, notwithftanding the extreme prolific powers of the 

 pucerons, we have reafon to be furprifed that their fpecies are not 

 entirely annihilated. On every leaf inhabited by the puceron we 

 find worms of different kinds. Thefe worms feed not upon the 

 leaves, but upon the pucerons, whom they devour with an almoft 

 incredible rapacity. Some of thefe worms are transformed into flies 

 with two wings, others into flies with four wings, and others into 

 beetles. While in the worm-ftate, one of thefe gluttonous infefts 

 •will fuck out the vitals of twenty pucerons in a quarter of an hour. 

 Reaumur fupplied a fingle worm with more than a hundred puce-» 

 rons, every one of which it devoured in lefs than three hours. 



Bcfide the general fyftem of carnage produced by the neceffity o£ 

 one animal's feeding upon another, there are other fources of de- 

 ftrudlon, which originate from very different motives. Man is not 

 the only animal who wages war with his own fpecies. War among 

 mankind, in certain accidental fituations of fociety, may be produc- 

 tive, to particular nations or communities, of beneficial effefls. But 

 8VQry advautage derived by war to one nation is acquired at the ex- 



