Vol. XIII 

 1896 



Thayer on Protective Coloration. 



125 



is responsible for most of the phenomena of protective coloration 

 except those properly called mimicry. 



Naturalists have long recognized the fact that the coloring of 

 many animals makes them difficult to distinguish, and have called 

 the whole phenomenon protective coloration, little guessing how 

 wonderful a fact lay hidden under the name. 



Mimicry makes an animal appear to be some other thing, whereas 

 this newly discovered law makes him cease to appear to exist at all. 

 The following are some examples of true mimicry. The Screech 

 Owl, when startled, makes himself tall and slim, and with eyes 

 shut to a narrow line simulates a dead stub of the tree on which 

 he sits. " Certain Herons stretch their necks straight upward, and 

 with head and green beak pointed at the zenith, pass themselves 

 off for blades of sedge grass. Certain harmless snakes spread 

 their heads out flat, in imitation of their poisonous cousins, and 

 rattle with their tails in the leaves. Many butterflies have stone 

 or bark-colored under sides to their wings, which make them 

 look like a bit of bark or lichen when they sit still on a stone or 

 tree trunk with wings shut over their backs. 



The newly discovered law may be stated thus : Animals arc- 

 painted by nature, darkest on those parts which tend to be most 

 lighted by the sky's light, and vice versa. 



The accompanying diagram illustrates this statement. Animals 

 are colored by nature as in A, the sky lights them as in B, 

 and the two effects cancel each other, as in C. The result is 

 that their gradation of light and shade, by which opaque solid 



