VARIABLE PROTECTIVE RESEMBLANCE IN INSECTS 137 



undergo no corresponding change of colour. How- 

 ever the adaptation arose in the ancestor of all butter- 

 flies which now emerge- from gilded chrysalides, it is 

 probable that it took place in some hot dry country, 

 where mineral surfaces did not weather quickly but 

 remained glittering for long periods of time. 



The manner in which golden chrysalides are adapted 

 for concealment on plants 



In the origin and gradual progress of our modern 

 aggressive forms of vegetation, less and less of the 

 land-surface has been formed by mineral substances, 

 until the green colour of foliage and the brown colour 

 of stems and of withered leaves have become the pre- 

 dominant tints of nature and the most feasible models 

 for Protective Eesemblance. It is therefore interesting 

 to note how the species with gilded pupse have adapted 

 themselves to the change. 



The chrysalis of the Peacock Butterfly (Vanessa lo) 

 still retains the dark variety, which is formed when 

 pupation takes place upon dark rock surfaces ; but the 

 golden form has been replaced by a green variety, 

 which is produced when the chrysalis is suspended 

 from the leaves of its food-plant. The green variety 

 still retains the metallic appearance, and exhibits it 

 to a much greater extent than the dark variety. 

 During the summer of 1888 I found that the green 

 form is produced by the surroundings which cause 



