30 NATURAL HISTORY. [CH. II- 



CHAPTER II. 



FURTHER OBSERVATIONS ON THE METAMORPHOSES OP IN- 

 SECTS, AS ILLUSTRATED IN THE BUTTERFLY. 



Theory of Swammerdam Theory of Herold Observations there- 



,,,.,,<, ^^^erflies ooy ran erescs ui^ ,. 



Double-brooded Insects Duration of the Life of Insects shortened 

 by Warmth, and prolonged by Cold Reaumur's Experiments 

 Irregular Period of Duration of Insects in the Chrysalis State 

 Periodical appearance of Butterflies. 



IN the preceding chapter we have seen that the 

 general theory respecting the transformations of in- 

 sects proposed by Swammerdam, and usually adopt- 

 ed, is, that the caterpillar, as soon as it has burst 

 from the egg, contains within its body the various 

 envelopes which present themselves on every 

 moulting of the skin during the caterpillar and 

 chrysalis state, as well as the butterfly itself. A 

 celebrated German physiologist, Dr. Herold, who 

 has studied the subject more closely than any natu- 

 ralist since the days of Swammerdam, Reaumur, 

 and Lyonnet, has, however, proposed an hypothesis 

 which appears to differ considerably from the pre- 

 ceding. According to this author, as quoted by 

 Kirby and Spence, " the successive skins of the 

 caterpillar, the pupa-case, the future butterfly, and 

 its parts and organs (except those of sex, which he 

 discovered in the newly-excluded larva), do not pre- 

 exist as germes, but are formed successively from 

 the rete mucosum, or mucous network, which it- 

 sell is formed anew upon every change of skin 



