CH. II.] METAMORPHOSES OF INSECTS. 41 



Reaumur had also recourse to a still more ing-e- 

 nious mode of causing the speedy disclosure of but- 

 terflies. In order to obtain a more regular supply 

 of heat than could be obtained from a stove, he 

 placed chrysalides in hollow balls of glass of the 

 size of an egg under a sitting hen, which would as 

 easily mistake them as round stones for her eggs ; 

 the results were similar to those in the former ex- 

 periment, the butterfly appearing in the course of a 

 few days. He omitted, however, to endeavour to 

 discover by experiment, whether by increasing the 

 temperature of the hothouse above summer heat he 

 could not produce them in fewer than thirteen days, 

 or whether a temperature beyond that of summer 

 would not destroy them. He likewise did not en- 

 deavour to discover whether, by nmintaining a con- 

 stant summer heat, a succession of broods could not 

 be obtained in the year, none of which should re- 

 main longer than thirteen days in the chrysalis 

 state, so that five or six different generations might 

 be produced in twelve months ; or whether in such 

 case the insect would not return to its natural 

 habits, and produce but two broods in the course of 

 a year. We mention these circumstances in the 

 hopes that some of our entomologists may be 

 tempted to pursue so interesting an investigation. 



Besides these, Reaumur tried a series of opposite 

 experiments, which we shall not detail, but by whicli 

 he proved, that by placing chrysalides in cellars or 

 icehouses at different periods of their existence, he 

 was enabled to prolong their duration in that state, 

 although he was at first fearful lest his chrysalides 

 would share the same fate with eggs kept too long, 

 and become addled. 



Not satisfied with trying the effects both of heat 

 and cold, this indefatigable naturalist was induced, 

 in continuance of a series of valuable experiments 

 upon the varnishing of eggs of hens, to varnish sev- 

 eral chrysalides, carefully covering every part of 



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