METAMORPHOSES. 41 



cnying animal and vegetable matter. For such agents an insatiable voracity 

 is an indispensable qualification, and not less so unusual powers of multipli- 

 cation. 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 egg, 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 existence. Having now laid up a store 

 of materials for the development of the future perfect insect, it becomes a 

 pupa; and during this inactive period the important process slowly pro- 

 ceeds, uninterrnpted by the calls of appetite. At length the perfect insect 

 is disclosed. It now often requires no food at all ; and scarcely ever more 

 than a very small quantity ; for the reception of which its stomach has 

 been contracted, in some instances, to a tenth of its former bulk. Its 

 almost sole object is now the multiplication of its kind, from which it is 

 diverted by no other propensity ; and this important duty being performed, 

 the end of its existence has been answered, and it expires. 



It must be confessed that some objections might be thrown out against 

 this hypothesis, yet I think none that would not admit of a plausible answer. 

 To these it is foreign to my purpose now to attend, and I shall conclude 

 this letter by pointing out to you the variety of new relations which this 

 arrangement introduces into nature. One individual unites in itself, in fact, 

 three species, whose modes of existence are often as different as those of 

 the most distantly related animals of other tribes. The same insect often 

 lives successively in three or four worlds. It is an inhabitant of the water 

 during one period ; of the earth during another ; and of the air during a 

 third; and fitted for its various abodes by new organs and instruments, and 

 a new form in each. Think (to use an illustration of Bonnet) but of the 

 cocoon of the silk-worm ! How many hands, how many machines does 

 not this little ball put into motion ! Of what riches should we not have 

 been deprived, if the moth of the silk-worm had been born a moth, without 

 having been previously a caterpillar ! The domestic economy of a large 

 portion of mankind would have been formed on a plan altogether different 

 from that which now prevails. 



I am, &c. 





