THE COLORATION OF ANIMALS 



79 



But as soon as the conditions that obtain among Lepidoptera are 

 also taken into consideration we recognize the insufficiency of the 

 interpretation suggested, for among butterflies we have precisely the 

 same phenomenon — sharp limitation of the protective colouring to 

 the parts visible in the resting position, a fact which, in the case of the 

 said buttei*flies, admits of no other interpretation than that of natural 

 selection. Let us therefore see if we cannot, in the case of Trojyido- 

 derus, arrive at some better understanding of the phenomenon than 

 that implied in the theory of direct light-influence. Obviously, the 



Fig. II. Tropidoderus chilclreni, after Bruuner von Wattenwyl, in flying pose. 

 V anterior wing. H. hdut, membranous jiart of posterior wing. H. horn, horny portion. 



yellow parts of the animal do not require to be green, since they are not 

 visible in the sitting position, and the locust in flight could not by 

 any device be made invisible. It therefore only remains to be 

 explained why the yellow parts are not colourless, and why they are 

 noji also green. We cannot at present answer with any confidence ; 

 it is possible that the colouring matter which causes the green only 

 becomes green under the influence of direct sunlight, and otherwise 

 remains yellow : it is possible, too, that, as in Lepidoptera (see 

 ^^S- 9)' the full protective colour is only developed by natural 

 selection in the places which are visible in the sitting position, and 



