METAMORPHOSES. 79 



A question here naturally presents itself — Why are 

 insects subject to these changes? For what end is it 

 that, instead of preserving like other animals "^ the same 

 general form from infancy to old age, they appear at 

 one period under a shape so different from that which 

 they finally assume ; and why should they pass through 

 an intermediate state of torpidity so extraordinary? I 

 can only answer that such is the will of the Creator, 

 who doubtless had the wisest ends in view, although 

 we are incompetent satisfactorily to discover them. Yet 

 one reason for this conformation maybe hazarded. A 

 very important part assigned to insects in the economy 

 of nature, as I shall hereafter show, is that of speedily 

 removing. superabundant and decaying animal and ve- 

 getable matter. For such agents an insatiable voracity 

 is an indispensable qualification, and not less so unusual 

 powers of multiplication. But these faculties are in a 

 great degree incompatible. An insect occupied in the 

 work of reproduction could not continue its voracious 

 feeding. Its life, therefore, after leaving the eg^, is 

 divided into three stages. In the first, as larva, it is in 

 a state of sterility ; its sole object is the satisfying its 

 insatiable hunger ; and, for digesting the masses of food 

 which it consumes, its intestines are almost all stomach. 

 This is usually by much the longest period of its ex- 

 istence. Having now laid up a store of materials 

 for the development of the future perfect insect, it 

 hecomes B. pupa ; and during this inactive period the 



* A few vertebrate animals, viz. frogs, toads, and newts, undergo me- 

 tamorphoses in si)me respects analogous to t!io:-e of insects; their first 

 form as tadpoles being very diflerent from that which they afterwards 

 assume. These reptiles too, as well as snakes, cast their skin by an opera- 

 tion somewhat similar to that in larva. There is nothing, however, im 

 their metamorphoses at all resembling the jf?J/;>a state in insects. 



