388 THE FHILOSOPHY 



The llbella, dragon, or lady-fly, is well known by ihe 

 beauty of its colours and the fymmetry of its form. For 

 thefe external qualities it has received the appellation of 

 lady-fy. Its difpofitions and its mode of life, however, are 

 more ferocious and waHike than thofe of the Amazones. 

 Like birds of prey, they hover about in the air, for the fole 

 purpofe of devouring alnioft every fpecies of winged infedl. 

 They accordingly frequent marfhy grounds, pools of water, 

 and the margins of rivers, where infects moil: abound. 

 Their appetite is fo grofs and voracious, that they not only 

 devour fmall flies, but even the large flefli-fly, moths, and 

 butterflies, of every kind. 



It has been often faid, that no animal fpontancoufly feeds 

 upon its ovs^n fpecies. This remark has probably been in- 

 tended as an apology for, or at leaft a limitation to, the gen- 

 eral fyftem of carnage eflabliflied by Nature. But the ob- 

 fervation, whatever might have been its intention, is unhap- 

 pily a refult of ignorance •, for fome quadrupeds, all fifhes, 

 and many infe(Sl:s, make no fuch difcrimination. The weak- 

 er are uniformly preyed upon by the ftronger. Reaumur 

 put twenty of thofe caterpillars which feed upon the leaves 

 of the oak into a vial. Though he regularly fupplied them 

 with plenty of frefli oak leaves, he obferved that the number 

 of dead ones daily increafed. Upon a more attentive exam- 

 ination into the caufe of this mortality, he found, that the 

 ftronger attacked with their teeth, killed, fucked out the 

 vitals of their weaker companions, and left nothing but the 

 head, feet, and empty flcins. In a few days, one only of the- 

 twenty remained in life. 



Caterpillars have myriads of external enemies, as birds of 

 almofl: every kind, mrjiy of the fmallar quadrupeds, their 

 own fpecies, and numberlefs infecfts. But this vaft fource 

 of devaftation is fl:ill augmented by what may be denominat- 

 ed their internal enemies. Many flies depofit their eggs in 



