Experiments of Grafin von Linden 
high temperature, in making it give rise to the 
prorsa form, and not to the /evana form, as it 
would ordinarily do. 
Similar results have been obtained with the 
seasonally dimorphic Pzerzs nafz. 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- 
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