INSECTS. 217 



is inconceivable ; and if it were not for the prodigious havoc 

 they made upon caterpillars and other insects, the fruits of the 

 earth would be entirely destroyed. Wasps are extremely fond 

 of animal food. They frequent butchers' stalls, and beat off 

 the flesh-fly, and every other insect that resorts thither for the 

 purpose of depositing its eggs in the meat. Butchers take 

 the advantage of this jealous warfare. They encourage the 

 wasps, and make sentinels of them by giving them livers, 

 which they prefer to more fibrous flesh, probably because they 

 can cut livers more easily with their teeth. 



The libella, dragon, or lady-fly, is well known by the 

 beauty of its colors, and the symmetry of its form. For these 

 external qualities it has received the appellation of lady-fly. 

 Its disposition and its mode of life, however, are more fero- 

 cious and warlike than those of the Amazons. Like birds of 

 prey, they hover about in the air, for the sole purpose of de- 

 vouring almost every species of winged insect. They ac- 

 cordingly frequent marshy grounds, pools of water, and the 

 margins of rivers, where insects most abound. Their appe- 

 tite is so gross and voracious, that they not only devour small 

 flies, but even the large flesh-fly, moths, and butterflies of 

 every kind. 



It has been often said, that no animal spontaneously feeds 

 upon its own species. This remark has probably been in- 

 tended as an apology for, or at least a limitation to, the 

 general system of carnage established by nature. But the 

 observation, whatever might have been its intention, is un- 

 happily a result of ignorance ; for some quadrupeds, all fishes, 

 and many insects, make no such discrimination. The weak- 

 er are uniformly preyed upon by the stronger. Reaumur put 

 twenty of those caterpillars which feed upon the leaves of the 

 oak into a vial. Though he regularly supplied them with 

 plenty of fresh oak leaves, he observed that the number of 

 dead ones daily increased. Upon a more attentive examina- 

 tion into the cause of this mortality, he found that the strong- 

 er attacked with their teeth, killed, sucked out the vitals of 

 their weaker companions, and left nothing but the head, feet, 

 and empty skins. In a few days, one only of the twenty 

 remained in life. 



Caterpillars have myriads of external enemies, as birds of 

 almost every kind, many of the smaller quadrupeds, their 

 own species, and numberless insects. But this vast source 

 of devastation is still augmented by what may be denomi- 

 nated their internal enemies. Many flies deposit their eggs 

 19 



