38 THE ENTOMOLOGIST. 



If these results are compared with mine, there can be no 

 doubt, but that the golden ground colour and the black are 

 actually in direct dependence on the height of the temperature, 

 which operates during the pupal period. 



The last experiment of Merrifield's especially appeared very 

 interesting to me, in which he first kept a portion of his pupsB 

 for 10 weeks on ice, and then brought them into 30° C, when 

 these pupge produced, after 5-6 days, butterflies of the summer 

 form, with black powdering and the narrow copper band of the 

 hind wings. It follows from this that the last days only of the 

 pupal period are decisive for these differences in colour, and that 

 neither the larval nor the whole of the first pupal period comes 

 into consideration. It could also be concluded from my second 

 experiment, that the temperature of the larval period had no 

 influence, as in this the larvae were kept at the same temperature, 

 and yet produced very different butterflies, according to whether 

 the pupae were subjected to cold or heat. But the fact, that the 

 temperature first produces these differences in colour in the last 

 5-6 days of the pupal development, confirms the conclusion 

 already drawn at the beginning, that it is not here a question of 

 the suppression of one of two different schemes of development 

 (Entwicklungsanlagen), but of a modification of the chemical 

 processes in the colour formation of the scale. But if it is cer- 

 tain, that a high temperature produces darkening, and moderate 

 cold a brightening, of the colour, still we have not yet exhausted 

 the whole process in this ; but it must be acknowledged that 

 local races exist, which react more strongly or less strongly to 

 the influence of cold or heat, and these local races correspond 

 in their manner of reaction to the climate, in which they live, 

 i. e. the races of warm climates are more readily accessible to 

 the influence of heat, than those of cold climates. This appears 

 to follow from my experiments, although, indeed, doubt might 

 be raised, as each of the experiments was made only once ; and 

 it must be admitted, that it is impossible in experiments to 

 entirely hit off the natural conditions of the insects, which develop 

 in the open. The change of the day and night temperature also 

 cannot be accurately produced, nor yet the degree of the humidity 

 of the air in the open ; it would consequently be conceivable, in 

 the abstract, that, if everything was closely imitated, just as dark 

 an eleus butterfly might arise from any German or even polar 

 pupa of phloeas, as from a Neapolitan one. The results of my 

 experiment B contradict, however, this suspicion, as they show 

 that the Neapolitan pupae produced some well-blackened eleus at 

 the ordinary room temperature in Germany, and many speci- 

 mens, which are, indeed, red, but which are all provided with 

 deeper black and larger black spots, than the German phloeas 

 exhibit as a rule. Also the Neapolitan pupa, kept on ice, pro- 

 duced, indeed, specimens which, in the small size of the black 



