METAMORPHOSES. 41 
caying animal and vegetable matter. Forsuch agents an insatiable voracity 
is an indispensable qualification, and not less so unusual powers of multiphi- 
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 arva, 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, uninterrupted 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 
anew 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 domestie economy of a large 
ortion of mankind would have been formed on a plan altogether different 
rom that which now prevails, 
Tam, &e. 
