312 INSECT TRANSFORMATIONS. 



ceeding August, 1735, at the time he was writing this 

 account, when he found them still living and heahhy, 

 but not transformed into perfect insects. We are not 

 aware whether he ever published the termination of 

 the experiment. 



In another instance, he placed in a coal-cellar the 

 pupae of the emperor-moth {Saturnia pavonia)^ about 

 a fortnight or three weeks before the usual time of 

 their evolution ; and they were in consequence retarded 

 to five or six weeks later than those of the same 

 brood which he had kept in his cabinet. The chry 

 salides of the large garden white butterfly (Pontia 

 Brassiccs), when placed in the cellar in January, 

 appeared two months later than those in the tem- 

 perature of the atmosphere. A still more decisive 

 experiment was made with the chrysalides of the 

 small tortoiseshell butterfly {Vanessa Urtica;), which 

 require fourteen days of summer heat to mature 

 them, and which, when hatched under a hen, had 

 appeared in four days. Some of these he placed in 

 the cellar the 12th of June, and they did not appear 

 till the 2nd and 3rd of August, — about six weeks later 

 than in their natural temperature. 



Reaumur, still haunted by the notion of the ex- 

 halation of moisture being the only cause of the 

 development of chrysalides, tried upon them similar 

 ingenious experiments to those which he had success- 

 fully made upon eggs, by varnishing them in order to 

 prevent the escape of moisture. His experiments 

 upon varnishing eggs have led to a most useful dis- 

 covery, now extensively acted upon in practice for 

 the preservation of eggs all over Europe. Those 

 upon chrysalides, however, were not conducted with 

 the same degree of acute accuracy. To prevent the 

 chrysalides from coming to maturity at the usual 

 time, by preventing the exhalation of their moisture, 

 he conceived it would be sufficient to varnish over 



