SOCIAL LIFE OF ANIMALS 487 



permanently. Herring of the same spawning form schools which 

 remain together permanently. 



References on Animal Relationships 



Alverdes, F. 1927. Social Life in the Animal World. Harcourt, 

 Brace & Co., Inc., New York. 



BoRRADAiLE, L. A. The Animal and its Environment. Henry Frowde 

 and Hodder and Stoughton. 



Cleveland, L. R. 1926. Symbiosis among animals with special refer- 

 ence to termites and their intestinal flagellates. Qu. Rev. of Biol., 

 vol. I, no. I, pp. 51-60. 



DoFLEiN, F. 1914. Das Tier als died des Naturganzen, from R. Hesse 

 and F. Doflein, Tierbau und Tierleben, Bd. 2. Leipzig and Berlin. 



Elton, C. 1927. Animal Ecology. Macmillan Co., New York. 



Protection 



Masking. — The caddis fly lives in a sand case. Certain crabs 

 cut off the tunic of a sea squirt and drape it over their carapace. 

 Others plant sea weed on their backs. 



Flounders cover themselves with sand while the toad puffer or 

 swell fish distends its body with air and escapes many enemies. 

 Other fishes cover themselves with sea weed. 



Color Resemblance. — Temporary alternations of color are due 

 to the amount of dilation of chromatophores. In the cuttle fish 

 and the squid we find that blushing occurs if they are irritated, 

 but they return to normal pale color shortly. 



Fishes, such as the flounder and the minnows, are able to adapt 

 themselves to the background. If they are blinded, color change is 

 impossible. Frogs, toads and chameleons are able to alter their 

 pigment {inelanophores) to suit the background, although Ditmars 

 holds that the chameleon is not immediately successful. 



Partridges and ptarmigans change their pigment to suit the 

 background. The arctic hare changes from brown to white when 

 winter comes. In the mammals we ^pjjgl that change in color de- 

 pends on the oxidation of melanin pigment. 



Some animals with a brilliant hue are bad tasting. The ex- 

 creted material makes the color bright. The skunk is an example 

 of a brightly colored form which has a distinctly obnoxious odor. 



Thayer, Poulton and others have emphasized the influence of 

 coloration on the survival of many animals. Except in the arctic 



