216 THE HARMONIES OF NATURE. 



to the influences of the weather. Besides, they are con- 

 stantly decimated by legions of enemies. Carnivorous and 

 parasitical insects of all sorts carabidae and hemiptera, telephori 

 and coccinellae, crabronidae and sphegidae, ichneumonidse and 

 tachini, libellulae and hemerobii are constantly chasing them; 

 all the warblers the swallow and the sparrow, the goat-sucker 

 and the woodpecker, the crow and the cuckoo devour them by 

 thousands ; the hedgehog and the mole, the bat and the hog, 

 the myrmecophaga and the armadillo, annihilate myriads 

 of larvae, caterpillars, ants, and termites ; and finally man, with 

 whom they are at constant war, strains all the resources of his 

 genius for their destruction. 



Thus, though they occasionally sweep over a country like a 

 hurricane or a pestilence, yet generally their ravages are 

 restrained within moderate bounds, and frequently prove 

 more beneficial than hurtful to the economy of the vegetable 

 kingdom. 



Many species chiefly attack such plants as are already diseased, 

 and by hastening their destruction promote the growth of a 

 more vigorous generation. 



An innumerable army of dung-beetles and stercoraceous flies, 

 of ants and termites, is constantly at work, removing the decay- 

 ing substances which would otherwise pollute the atmosphere ; 

 and even the gnats and mosquitos, whose bristly stings inflict 

 such misery upon man, are in another respect his benefactors, as 

 their larvae cleanse the stagnant waters of the swamps and 

 morasses, and thus prevent many noxious exhalations. 



The existence of numerous birds and quadrupeds depends 

 upon that of the insects, which are their exclusive food; and if 

 the caterpillars often prove a source of great annoyance to the 

 gardener, we must not forget that were the insects removed, the 

 nightingale, the redbreast, and other delightful songsters of 

 the fields and groves would likewise perish. 



Thus the insects indirectly contribute to our enjoyments, and 

 several of them are of such direct importance as to play a 

 considerable part in the annals of commerce. The silk- 

 worm, the cochineal, and the bee enrich whole nations, and 

 give employment to numberless artisans. The gallnuts, a not 

 unimportant article of trade, are produced by the sting of a 

 wasp (Cynips tinctoria) on the leaves of the gall -oak ; and the 



