164 



SECTION I. 



ON THE PRINCIPLES WHICH REGULATE THE METAMORPHOSES 

 OF INSECTS. 



It is owing, as already stated, to the developement of 

 wings that the Ptilota, or winged insects, are necessarily 

 subjected to a more complete and astonishing series of trans- 

 formations than the other annulose animals, in which the 

 changes (to which, in fact, in a greater or less degree, all 

 animals are subject) merely consist in a periodical casting off 

 of the outer envelope. 



It is true that in a few insects, which are evident excep- 

 tions to the general rule, the same mode of moulting takes 

 place as in the other annulosa. Owing to the external 

 envelope of these animals constituting their skeleton, and 

 oiFering, from its stronger consistence, a complete obstacle 

 to the increase in size of the inclosed animal, it is necessary 

 that this skeleton should from time to time be cast off. 

 We have, therefore, in the first place, to inquire how 

 the animal which throws off so important a portion of its 

 organs as its skeleton can exist, or in what manner a new 

 skeleton is formed. Swammerdam, in his really wonderful 

 series of observations, discovered, in his endeavours to prove 

 that all insects are produced from eggs, and that the cater- 

 pillar was but an immature butterfly, that shortly previous 

 to changing to a chrysalis, the various parts of the butterfly 

 were found distinctly incased beneath the skin of the cater- 

 pillar ; and thereupon he has raised the theory which has 

 been generally adopted by subsequent authors, that every 

 caterpillar, at its first existence, contains within itself the 

 germe of the futm-e butterfly, and all its envelopes, which, 

 successively presenting themselves, are thrown ofi", till it 

 attains its perfect winged state. This theory has, however, 

 been completely opposed by Dr. Herold, a distinguished 



