NATURAL SELECTION IN ACTION 



367 



FIG. 16.1. Dark-colored (melanic) and 

 light-colored "typical" specimens of the 

 peppered moth (B/s/on befularia) at rest 

 upon o lichen-covered tree trunk. (Photo- 

 graph by courtesy of Dr. H. B. D. Kettle- 

 well.) 



FIG. 16.2. Light-colored "typical" and 

 dark-colored (melanic) specimens of the 

 peppered moth (6/'sfon befularia) at rest 

 upon a lichen-free, blackened tree trunk 

 in an industrial region. (Photograph by 

 courtesy of Dr. H. B. D. Kettlewell.) 



graphically, that birds do search out and eat motionless moths on tree 

 trunks, a fact that had been doubted. This being true, does coloration 

 which renders moths inconspicuous to our eyes also serve to protect them 

 from being seen by birds? Careful observation indicates that the coloration 

 is of protective value. Thus Kettlewell and his colleagues kept eighteen 

 moths under continuous observation. Nine were of the light form, nine of 

 the dark, and they were all on blackened tree trunks. During the day of 

 observation all nine of the light individuals were found and eaten by 

 birds but only three of the dark individuals were. On another occasion a 

 pair of redstarts and their young were observed for two days in a polluted 

 locality. Light and dark moths had been reared by the experimenters and 

 were released in equal numbers. During the two days forty-three of the 

 light individuals were found and eaten but only fifteen of the dark ones 

 were. On the other hand, similar observations in unpolluted countryside 

 yielded results which were just the reverse. Again the light and dark indi- 



