38 ZOOLOGY 



show adaptation in color and form witli reference to their 

 en\'ironment. The case of leaf and sticlv insects has been 

 referred to on page 18. Grasshoppers found on beaches and 

 other sandy areas are much lighter than the same species in 

 grassy meadows. Some of the true bugs, which hve on 

 shrubs, resemlDle thorns. Some flies (page 82) mimic bees in 

 shape and the humn:iing sound that they make ; and certain 

 beetles almost exactly resemlile the bark and lichens on which 

 they occur. Among mammals and birds the stripes with 

 which their coat or plumage is marked serve to break the 

 uniformity of coloration in the same way that the lights and 

 shadows break the uniformity of a landscape. The striped 

 animals l^lend into the landscape and so become inconspicuous. 

 The s])ots on certain deer closely resemble the flecks of 

 sunlight in the forest (Fig. 39). The light color of the 

 under part of animals serves to reduce the effect of sliade and 

 so to do away with the sudden transition lietween the ground 

 and the animal's bod}' (Fig. 361). ]\Iany of the lower 

 groups of animals, such as fishes and lizards, are able to 

 change the color of their bodies so as to make them harmo- 

 nize with their background. Thus the flatfishes or flounders 

 are much lighter when they rest on clear sand than when they 

 rest on muddj^ bottoms, and crabs, by perniitting the growth 

 of seaweed on their backs, become hidden from their 

 enemies. Other inhabitants of brilliantly colored coral 

 reefs have the colors of coi'al. Thus adaptations in color and 

 form are "\\'ides])read, and the gmieral theorj' express(>d 

 in the preceding paragraph serves to account for them 

 wherever found. But it would lie rash to assert that every 

 detail of form or color had been determined by the struggle 

 for existence. 



