CH. II.] METAMORPHOSES OF INSECTS. 39 



found by experience that those drops were not found 

 on the house-tops nor upon the round sides of the 

 stones which stuck out, as it would have happened 

 if blood had fallen from the sky, but rather where 

 the stones were somewhat hollowed, and in holes 

 where such small creatures might nestle and shroud 

 themselves. Moreover, the walls which were so 

 spotted were not in the middle of towns, but they 

 were such as bordered upon the fields ; nor were 

 they on the highest parts, but only so moderately 

 high as butterflies are commonly wont to fly." 



The period in which an insect remains in the 

 chrysalis state is not always of the same duration, 

 although at the same period of the year it is similar ; 

 for instance, those caterpillars of the swallow-tailed 

 butterfly which are changed into chrysalides about 

 the middle of July, appear as butterflies at the end 

 of thirteen days, while those which appear in the 

 caterpillar state at the beginning of September re- 

 main during the winter in the chrysalis, and do not 

 become butterflies until the spring. " Thus," says 

 Reaumur, " here is one butterfly which only remains 

 thirteen days in the chrysalis state, while another, 

 precisely similar, requires nine months to bring it 

 to perfection, just as though the inhabitants of cold 

 regions were to live four or five centuries, while the 

 life of those dwelling under the equator was only to 

 be extended to its ordinary length : hence it is evi- 

 dent that it is by evaporation or combination of the 

 fluid parts of a chrysalis, produced by the applica- 

 tion of heat, that the insect is brought to its perfect 

 state much quicker at one period of the year than at 

 another." 



Conceiving, therefore, that the butterfly is not in 

 a state to burst from the chrysalis until by the ac- 

 tion of heat and insensible perspiration a certain 

 quantity of superabundant humidity has evaporated, 

 and the other fluid parts of the body become assimi- 

 lated, Reaumur came to a conclusion, that in pro- 



