ADAPTATIONS 431 



when sitting quietly is not readily seen. She is, therefore, 

 probably less frequently molested. The male is free to take 

 to flight when discovered and pursued. The color of the female 

 is explained on the basis of ordinary natural selection, while 

 that of the male is due to the operation of sexual selection. 



863. Protective Resemblance. In many cases the animal 

 resembles its environment in form as well as color. This is 

 called protective resemblance. There are insects which 

 resemble dead twigs, rolled and broken dry leaves, dead 

 leaves still on the twig, green leaves, seed pods, patches of 

 lichens, etc. There are fishes which resemble sea weeds and 

 even a mammal, the sloth, resembles a lichen-covered knot on a 

 tree. 



864. Feigning. Many animals when threatened by enemies 

 resort to bluff. They assume terrifying attitudes, make a show 

 of great size by swelling themselves or raising hair or feathers 

 on end, or make disconcerting noises like hissing, spitting or 

 growling. Feigning death or "possuming" is another com- 

 mon instinctive method of getting out of a tight place. The 

 opossum is a well-known example and has lent his name to 

 this particular instinct. Beetles often feign death. When 

 attacked they allow themselves to fall to the ground and lie 

 there motionless for some time. They are then difficult to 

 find, whereas if they attempted to run or fly their move- 



The three types of female Papilios, shown on the left in B, C, and D, belong to 

 the same species, of which the male is represented in A . There is also a type of 

 female which resembles the male, and still another form which is not figured 

 here. There are then five types of females within this species. Three of these, 

 beside the male, have been reared from the same brood of eggs. This species 

 is found in Africa but a similar case of polymorphism is found in India. The 

 origin of the polymorphism in this case is apparently due to mimicry. The 

 species of Amauris and Danais represented on the right in the figure are pro- 

 tected, i.e., they are unpalatable to birds, hence the female Papilios by mimicry 

 also secure immunity from the attacks of birds though they are not otherwise 

 protected. The males are not protected, nor are they mimics, but they are pro- 

 duced in much greater number than the females. In A the predominant color 

 is yellow, in C it is orange, while in B and D it is white, or pale yellow, and dark 

 gray to black. Xi/2. 



