114 THE BUTTERFLY VIVARIUM. 



days to two or three or more years, the smaller 

 kinds, in general, undergoing their changes more 

 rapidly than the large ones. The influence of tem- 

 perature is much more apparent in the case of chry- 

 salides than it is with eggs, as satisfactorily proved 

 hy Reaumur. He placed a numher of chrysalides 

 in a hot-house in January, which under natural cir- 

 cumstances would not have given forth the perfect 

 insect till May ; hut which, influenced hy the arti- 

 ficial heat, opened within fourteen days. A contrary 

 experiment was equally successful; a numher of 

 chrysalides placed in an ice-house heing retarded 

 during a whole year. It should he stated that those 

 raised hy heat were all healthy, and bred and laid 

 their eggs, which were successfully hatched. This 

 sufficiently demonstrates the possibility of rearing 

 splendid tropical species with the assistance of arti- 

 ficial heat, as described in my Chapter upon that 

 subject. 



To return to the consideration of the time 

 passed in the pupa state under ordinary circum- 

 stances, I may remark here that seemingly inexpli- 

 cable variations in this respect occur in the same 

 species. Out of a batch of chrysalides, of the same 

 brood, the great majority will open at the usual 

 time ; but some few will invariably remain in the 



