VARIATION AND ABERRATION IN BUTTERFLIES. 109 



of V. io was in these instances entirely lost, and the under side 

 acquired a much greater resemblance to that of V. urtkce or 

 T^ pohjchloros, L. 



Besides these forms showing a transition to V. urticm, L., a 

 form was also produced exceptionally (properly therefore an 

 aberration) which may occasionally be met with in nature. Its 

 chief peculiarities are the enlargement of the black costal spot 

 internal to the ocellus of the fore wing, the darkening of the 

 inner part of that ocellus, and the disappearance of the ocellus 

 from the hind wing. 



6. V. antiopa, L. 

 A species which reacts to different degrees of temperature 

 hardly less markedly than V. io, and on this account of the 

 highest interest. 



a. Warmth. 



Pupffi exposed for 48 hours to 37° C. (98°— 99° F.) yielded the 

 perfect insects 10 days later in the room. 



In these the blue of the outer margin seemed to be more or 

 less reduced. 



On the hind wing the yellow outer border, especially from the 

 tail-like projection to the dorsal (anal) angle, is broader than in 

 normal specimens, which leads to a displacement inwards of the 

 blue and also of the ground colour of the wing. 



On the fore wing the yellow reaches in a wavy or simply 

 arched form up to the row of blue spots, in this manner more or 

 less crowding them out. No very characteristic variation of 

 aspect, however, from the typical form of the species occurs in 

 these examples l3y the mere fact that the blue points undergo a 

 very marked reduction, even to the size of a large pin's-head, as 

 is the case in a series of my specimens, or even, as in a few 

 individuals, to still smaller dimensions ; for both the ground 

 colour and the outer border scarcely differ in any appreciable 

 degree from the normal colouring of the species. 



The hind wing also shows no difference as compared with the 

 type-form, except for the slight blackening of the margin. 



But under the above-mentioned treatment of the pup^e of 

 V. antiopa there arose among the specimens just described, in a 

 few isolated instances only (about 2 per cent.), another divergent 

 and very remarkable creature, which may accordingly be spoken 

 of as a true "aberration." This I shall at once describe more 

 minutely, as under another kind of treatment of the pupa the 

 same form occurs constantly, — becoming, therefore, a true 

 "variety." 



Pupte of V. antiopa exposed for 60 hours to a temperature of 



37" C. (98°— 99° F.), and then kept at 24° C. (75° F.), produced, 



12 days after pupation, a butterfly which, among all the forms 



hitherto obtained by me in these experiments, departed most 



ENTOM, — APRIIi, 1895, l4 



