650 



ECOLOGY AND EVOLUTION 



to respond diflFerentially to environmental 

 backgrounds. In this experiment other pos- 

 sible characters than the color relationship 

 seem to have been well controlled. The 

 capacity for plasticity of color response and 

 adaptive coloration are both known to be 

 genetic and different in closely related 

 species. 



Isely (1938) tested various colored 

 species of grasshoppers on various colored 



in this case color may be modified by rais- 

 ing the young of the same species on dif- 

 ferent background colors (Faure, 1932; 

 Hertz and Imms, 1937; James, 1944). Such 

 plastic color differences would not be sub- 

 ject to evolutionary diversification, but the 

 genetic difi^erential in capacity to react to 

 background color could evolve. 



Dice (1947) performed a number of ex- 

 periments on predator selection. He sub- 



Fig. 236. A praying mantis resembling the green leaves among which it lives in Panama. 



(Photograph by Ralph Buchsbaum.) 



backgrounds against the predatory activi- 

 ties of chickens, turkeys, and native birds. 

 The nonprotected forms that did not match 

 their backgrounds were eaten more readily 

 than those that were protected by back- 

 ground resemblance. Four hundred and 

 five, or 88 per cent, of the nonprotected 

 forms were eaten, in contrast with fifty-four, 

 or 12 per cent, survivors; 183, or 40 per 

 cent, of the protected forms were eaten, in 

 contrast with 276, or 60 per cent, survivors. 

 The differences between grasshopper spe- 

 cies are probably largely genetic, although 



jected genetic strains of the mouse, Per- 

 omijscus maniculatus, that varied in color, 

 to owl predation (of Asio wilsoniamis and 

 Tijto alba pratincola) at various light inten- 

 sities on different colored soils. The mice 

 were given some protection by letting 

 them run under a "jungle" of sticks form- 

 ing a latticework 3? to 4h inches above the 

 floor. This "jungle" forced the owls to cap- 

 ture the mice by sight rather than hearing. 

 Mice that matched their background soils 

 had a great selective advantage, compared 

 to those not so concealed. For example, the 



