44 NATURAL HISTORY. [cH. II. 



season, twelve others appeared at the end of two 

 years, and the remaining twelve at the end of three 

 years. Heineken also relates that he kept several 

 pupae of the large emperor moth through the win- 

 ter in a room heated daily by a stove, and several 

 others in a cold chamber, and that some of each 

 parcel appeared in March, while others had not ap- 

 peared in July, although still in a healthy condition. 

 In England this moth appears, in its natural state, 

 in the months of April and May, and again in Au- 

 gust. As, however, we do not find it recorded by 

 Haworth or Stephens that this is one of the double- 

 brooded moths, it appears to us probable that Heine- 

 ken's remaining specimens would have appeared in 

 the following August. But if this were the case 

 with Heineken's specimens (and this supposition 

 will enable us to account for the appearance of the 

 British specimens in August), to what is it owing 

 that a portion of the same brood should remain 

 three or four months longer in the chrysalis than 

 the remainder of the brood; the case being usually 

 very different with those specimens which remain 

 longer in the chrysalis, for these make their appear- 

 ance at the same time of the year as their elder 

 brethren 1 We may probably account for the cir- 

 cumstance mentioned by Heineken, that those placed 

 in the heated room did not appear earlier than those 

 kept in the cold, by supposing that the heat was not 

 maintained during the night, and that even in the 

 daytime it might not have greatly exceeded that 

 temperature of the atmosphere. 



Respecting the periodical appearance of insects, 

 the Cicada septemdecim, subsequently noticed, which 

 is said to make its appearance only once in seven- 

 teen years, affords one of the most striking exam- 

 ples ; but there are several of the British butterflies 

 which are not less remarkable. Among these, the 

 painted lady butterfly {Cynthia cardui) is eminently 

 conspicuous, occurring in the neighbourhood of the 



