346 The Theory of Natural Selection 



At the same time, bees and wasps are particularly scarce in 

 this region, so that flies are deprived of whatever advantage 

 they might theoretically derive from their resemblances to 

 the stinging insects since there are not enough of the latter 

 in the region to teach the birds to let them alone. 



Chance Resemblances 



Aside, however, from the speculative interpretation of 

 natural resemblances, we have acquired more recently some 

 definite information on the inheritance of color and pattern, 

 particularly in insects. Among certain tropical butterflies, 

 the male and the female have different patterns of wings. 

 In one of these groups there are several distinct female 

 types. One of the female forms resembles most closely the 

 male of the species; but each of the others may be said to 

 mimic two or three other species (Fig. 88). By means of 

 breeding experiments, it has been shown that the pattern of 

 wings in these animals is determined by several distinct fac- 

 tors, which are inherited in a definite way (page 274) . The 

 theory of mimicry as having developed through natural 

 selection, because of the protective value, is plausible enough. 

 It suffers, with the rest of the natural selection theory, in 

 disregarding entirely the sources of those variations that 

 make differential death rates possible. How does a par- 

 ticular appearance, color or form arise in the first place? 



Many years ago the late Dr. Bashford Dean collected 

 a large number of natural objects on which could be dis- 

 cerned more or less distinctly a figure suggesting a human 

 skull. He elaborated from this material the absurdity of 

 attributing to a particular pattern the adaptive advantage 

 which Darwin's theory presumed. The death's-head pattern 

 on a moth's wing or on the back of a crab may look suffi- 

 ciently like a skull to frighten a human being who is 

 frightened by such an image. To assume that this pattern is 

 present on the wing of the moth because of a special advantage 

 seems rather far-fetched. The same pattern is also to be 



