undergone hy Insects in the Pupal State. 



303 



anticipated from the conclusions previously set forth. This 

 result is, I think, sufficiently curious to warrant insertion : — 



It is here seen that the size of the variety is directly 

 instead of inversely proportional to the ratio of the pupal to 

 the larval period and vice versa. Whether these results are 

 due to mere coincidence or whether they are related as cause 

 to effect I am quite unable to say. The calculations, however, 

 point to the conclusion either that the pupal waste has no effect 

 upon the size of the imago, or else that it is overbalanced by 

 the action of other causes. The difference of size between 

 Walshii, Telamonides, and Marcellus is therefore most probably 

 correlated with those other differences (such as marking of 

 imago, pattern and colour of larva, duration of egg-stage, &c.) 

 which Mr. Edwards has shown to exist between these three 

 varieties. 



Double-brooded species appeared also to present at first 

 sight data fitted for testing the conclusions arrived at ; but 

 further reflection convinced me that such facts as are known 

 are so encumbered by factors of unknown value as to render 

 their comparison useless. Thus the species of Selenia and 

 Ephyra inhabiting this country are double-brooded, the indi- 

 viduals of the spring brood being in both cases larger than 

 those of the autumnal brood. Now the spring brood passes 

 the whole winter in the pupal state, while the autumnal brood 

 passes only a few weeks in the summer in this condition. In 

 this case temperature is the unknown disturbing factor. We 

 know not the amount of the total loss either during the summer 

 or winter pupal period ; neither do we know the amount of 

 the total gain of the larva during its vernal period of feeding 

 or during its autumnal period of feeding. With Selenia also 

 there is some difference of colour and marking between the 

 two broods ; so that we have here " seasonal dimorphism," 

 with Avhich, as in P. Ajax, the difference of size may be corre- 

 lated. The European butterfly Araschnia prorsa is also 

 double-brooded : but in this case the spring variety is the 



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