INDIRECT BENEFITS DERIVED FROM INSECTS. 235 



proach, it drives them away, and it is continually engaged in 

 catching case-worm flies and other insects (for the species of 

 this tribe all catch their prey when on the wing, and their 

 large eyes seem given them to enable them the more readily 

 to do this,) that fly over the water, pulling oft" their wings 

 with great adroitness and devouring in an instant the contents 

 of the body. From the number of insects of this tribe which 

 are every where to be observed, we may conjecture how useful 

 they must be in preventing too great a multiplication of the 

 other species of the class to which they belong. 



Lastly, under this head, not to dwell upon some other apte- 

 rous genera, devourers of insects, as the scorpion and centipede, 

 Phalangium, Galeodes, must be enumerated the whole world 

 of Spiders, extremely numerous both in species and individuals, 

 which subsist entirely upon insects, spreading with infinite art 

 and skill their nets and webs to arrest the flight of the heedless 

 and unwary summer tribes that fill the air, which are hourly 

 caught by thousands in their toils ; one of them ( Theridium 

 l^-guttatum Rossi), we are told, even attacking the redoubted 

 Scorpion. ^ 



So much for the insect benefactors to whom it is given in 

 charge to keep the animals of their own class within their 

 proper limits ; and I cannot doubt that you will recognise the 

 goodness of the Great Parent in providing such an army of 

 counterchecks to the natural tendency of almost all insects 

 to incalculable increase. But before I quit this subject I 

 must call your attention to what may be denominated cannibal 

 insects, since, in spite of those declaimers who would persuade 

 us that man is the only animal that preys upon his own species ^, 

 a large number of insects are guilty of the same oflence. 

 Reaumur tells us, that having put into a glass vessel twenty 

 caterpillars of the same species, which he was careful to supply 

 with their appropriate food, they nevertheless devoured each 



1 Thiebaut de Berneaud's Voyage to Elba, p. S 1 . 



2 " Even Tiger fell and sullen Bear 



Their likeness and their lineage spare. 

 Man only mars kind Nature's plan, 

 And turns the fierce pursuit on Man ! " 



Scott's Rokehij, canto iii. I. 



