VARIABLE PROTECTIVE RESEMBLANCE IN INSECTS 135 



roundings shows that they are essentially protective, 

 and as far removed as possible from conspicuous 

 warning colours, the object of which is to render their 

 possessors unlike the environment. What can be the 

 object in nature which the glittering pupae resemble ? 

 It is obvious that metals are not sufficiently abun- 

 dant on the surface of the earth to afford models for 

 successful imitation, and there is the same objection 

 to certain metallic sulphides which otherwise would 

 answer the purpose admirably. 



A consideration of the darker non-glittering va- 

 rieties of the same species helps us to an explana- 

 tion. These certainly resemble the grey surface of 

 weathered rocks, and the whole shape of such pupae, 

 with their angular projections and tubercles, com- 

 bines with their colour to produce a most perfect 

 Protective Kesemblance to rough dark surfaces of 

 rock. In fact, did we not delude the larvae by offering 

 them flat mineral surfaces in our walls and sides of 

 houses, the protection would be so complete that 

 we should hardly ever find the chrysalides ; and, as 

 a matter of fact, they are rarely seen except in such 

 situations. 



In England we very rarely see a brightly metallic 

 pupa because in our moist climate exposed rock- 

 surfaces quickly weather and become lichen-covered. 

 If, however, the bright appearance of many recently 

 fractured rocks were retained, as they are in drier 

 countries, they would cause the production of a similar 



