No. 571] TERRESTRIAL ASSOCIATIONS 



427 



abundant. Few animals are really non specialized in 

 habits; many moderately specialized species, however, 

 may on occasion turn from their ordinary activities, per- 

 haps to appropriate a particularly abundant kind of food. 

 Many ants are thus habituated to certain ordinary kinds 

 of food, but are able to eat organic food of almost any 

 sort, and do vary their food with circumstance. When, 

 as frequently happens, some animal species becomes very 

 abundant, 4 the attacks of a great many species of flexible 

 habits becomes concentrated upon it, and the numbers of 

 the food-species are soon reduced to normal. Animals 

 with non-specialized habits, by taking whatever food is 

 easiest of access, act as regulators of disturbances within 

 the association. A clear exposition of the manner in 

 which species of generalized habits restore unbalanced 

 conditions to equilibrium is given in a paper by Forbes 

 (1883), in which the regulative action of birds upon 

 insect oscillations is discussed. 



The animal's status within the association is deter- 

 mined not only by its food-habits, but by the sum-total of 

 its physiological and behavior characters (its mores). 

 The degree of dominance is indicated not merely by the 

 degree of specialization of food-habits, but in all habits, 

 by the degree of flexibility of behavior. An extreme 

 specialization in nearly any behavior character, as habit 

 of abode in the pit-digging ant-lion larva, prevents the 

 species from becoming dominant. The degree of spe- 

 cialization of behavior is thus a convenient criterion of 

 the relative influence of animals in the association. The 

 dominant animals are moderately specialized, and carry 

 on the ordinary work of the association. The highly spe- 

 cialized animals make use of spare otherwise unoccupied 

 and food material not demanded by other species. Cer- 

 tain of the first group, with habits more highly regulatory 

 than is usual, with perhaps some few unspecialized forms 



