EXPERIMENTS ON INSECTS. 311 



other insects, he tried all the preceding experiments 

 with very similar results. The heat communicated to 

 the glass egg was very cunsiderable, amounting lo 

 31° or 32^ of Reaumur's thermometer,* or about 100^ 

 Fahr. It was not surprising, therefore, that some of 

 the pupa; perished : we thbk it more wonderful that 

 any of them survived. 



ROaumur suggests, from these experiments, that 

 those who are curiuus in obtaining the productions 

 of summer during winter, may add to the gaiety 

 of their forced flowers, by forcing a brood of butter- 

 flies into life to sport amongst them ; and he records 

 an instance in which a friend of his at Strasburgh in 

 this way hatched, by means of a stove, all the pupae 

 he could obtain. We have in several instances suc- 

 ceeded in obtaining butterflies in winter, by keeping 

 chrysalides under glasses on a mantel-piece in a room 

 with a constant fire; but during the winter of 1829-30, 

 all which were thus kept died, probably from the fires 

 required by the unusual severity of the season being 

 too great for them. Several, on the other hand, 

 which we found on walls, and which had been ex- 

 posed to all the rigours of the winter, were disclosed 

 in due time in a perfect state. 



Having thus ascertained that heat produced the 

 effects which he had anticipated, Rt'aumur next tried an 

 opposite series of experiments, by placing chrysalides 

 in diminished temperatures. He accordingly en- 

 closed in nurse-boxes a number of pupa; formed in 

 August 1733, and in the following January placed 

 them in a coal-cellar : their natural period of appear- 

 ing in the perfect state being July 1734. During the 

 hot months of this year he went from time to time to 

 see whether these pupre indicated an approaching 

 change, but they remained in their original state 

 during July and August, and continued so till the suc- 



* Reaumur, ."Mem. vol. ii, p. 17. 



