538 



TENTH CHAPTER. 



INSECTS IN RELATION TO OTHER ORGANIC 



BEINGS. 



301. 



IT is a proved fact that all animal bodies derive their nutriment 

 originally from the vegetable kingdom. In no class of animals is this 

 more evident to us than among insects. We have before seen, where 

 we spoke of the food of insects, that vegetable substances constitute 

 their chief subsistence, and that entire orders, as, for instance, the 

 Lepidoptera, from the first moment of their existence, feed upon 

 nothing but plants and their juices. In the innumerable multitudes 

 of different species, and the hosts of individuals of one species, this 

 might eventually prove injurious to the vegetable kingdom, if also 

 many insects did not t likewise aid to promote the growth of plants. 

 This observation leads us to recognise the true relations of the insect to 

 the vegetable world, and whilst discovering this we perceive at the 

 same time the precise object nature accomplishes in its capacious 

 economy by means of insects. It is double ; in the first place to set a 

 limit to the preponderating increase of plants, and also, as such a rela- 

 tion might easily degenerate into their total destruction, it is also 

 careful, by another course, of preserving the vegetable kingdom. 



The first object is attained by means of those insects which derive 

 their nutriment from vegetable substances, consequently by means of 

 those which devour leaves, flowers, wood, fruits, and their seeds. These 

 organs provide for the continuance of plants as individuals or species, 

 and, every plant would more or less suffer if one or all of them were 

 totally destroyed by insects. Let us examine this more closely in indi- 

 vidual instances. 



302. 



With respect to those insects which destroy the roots of many plants, 

 and thereby restrict their superfluous growth, we must remark, that it is 

 generally larvae only which feed upon that part. Among the Carabodca 



