136 THE COLOUES OF ANIMALS 



appearance in the pupae of those larvae which sought 

 them. 



Although metallic surfaces are not conspicuous in 

 nature, there is a very abundant glittering mineral 

 which is quite common enough to offer a surface 

 against which the larvae might often suspend them- 

 selves. I refer to the mineral mica, the substance 

 forming the glittering flakes which are so well-known 

 in common granite. Furthermore, any recently 

 broken rock contains bright and glittering surfaces, 

 although they may not be so brilliant as mica, and 

 the bright spots of the pupae would thus be of pro- 

 tective value against almost any freshly exposed 

 mineral surface. 



Hence we see that the pupae would occur as dark 

 or glittering forms, as the surrounding mineral sur- 

 faces are dark or glittering : they appear in two 

 different varieties which are respectively in harmony 

 with the two conditions of the mineral surfaces they 

 resemble the dark and weathered, and the bright 

 and freshly exposed condition. 



It may be that this adaptation to mineral sur- 

 roundings arose when the widespread green tints of 

 the vegetable kingdom contributed less to the total 

 appearance of land-surfaces ; or the adaptation may 

 have followed the habit of feeding upon herbaceous 

 plants which withered away in the hot season, 

 changing from green to brown during the time when 

 the insect was in the chrysalis state and could 



