Experiments of Grafin von Linden 



high temperature, in making it give rise to the 

 prorsa form, and not to the levana form, as it 

 would ordinarily do. 



Similar results have been obtained with the 

 seasonally dimorphic Pieris napi. Standfuss, 

 the Grafin von Linden, and others have obtained 

 like results in the case of other seasonally di- 

 morphic butterflies. In some instances it has 

 been proved that the change in the pigment is a 

 purely chemical one ; a similar transformation 

 can be effected in the extracted pigment. But, 

 we must bear in mind that the changes which 

 are induced in this way are not confined to 

 colour ; they occur in the marking and shape of 

 the wing. 



Even more remarkable is the fact that in some 

 sexually dimorphic species a change of tempera- 

 ture alters the female, so as to cause her to have 

 the outward appearance of the male. For 

 example, it has been found that warmth changes 

 the colours of the female Rhodocera rhamni and 

 Parnassius apollo into the colours of the male. 



By applying rays of strong light, electric 

 shock, or centrifuge, the Grafin von Linden was 

 able to change the colours of the butterflies to 

 which the caterpillars gave rise. Pictet experi- 

 mented on twenty-one species of butterflies, or 

 rather on their caterpillars, and found that in 

 nearly all cases when the caterpillars ate unusual 

 food, they developed into butterflies with ab- 



