116 COACTION: THE INTERRELATIONS OF ORGANISMS 



pattern of food chains, especially because of its basic significance in 

 the biotic community. It further seems desirable at present to employ 

 the term for any particular grouping of food chains rather than all 

 those of a community, owing to the vast number at present in an 

 extensive community. 



In the treatment that follows, an endeavor is made to keep the 

 dynamic viewpoint constantly to the fore. The chief purpose is to 

 present a flexible arrangement that can be utilized to reveal the signifi- 

 cance of each process in the working of the community as a whole. 

 The length to which food '?oactions are discussed is not to be con- 

 strued as indicating an importance greater than shelter or other coac- 

 tions, but rather that the extensive available facts have been brought 

 together and classified to form a pattern for the study of other 

 coactions. 



The plant population changes more or less completely with each 

 stage in succession on land. For a number of stages, the species in- 

 crease steadily and there is a corresponding increase in the variety 

 and amount of shelter and food produced. In grassland, this may 

 continue into the climax, but as a general rule, and particularly in 

 coniferous forest, there is a marked reduction in both quantity and 

 variety as the climax is approached. The usual consequence is a 

 similar decrease in the kind and number of animal consuments, so 

 that climax forests are often peculiarly monotonous in terms of bird 

 and mammal or even insect influents. Conversely, the subclimax 

 areas are relatively rich in major influents because of the great variety 

 of shelter and materials, as well as food. Hence, it is sometimes both 

 desirable and convenient to refer to food nexes as climax or serai 

 when significant differences exist between them. 



ANIMALS AS ACTIVE AGENTS (COACTORS) 



The major distinctions between animal coactors are founded upon 

 taxonomic life forms primarily, often with important subdivisions on 

 the basis of life-history stages, as in metamorphic insects, and of 

 behavior types such as are found in many groups. With respect to 

 community significance, the general classification into herbivores 

 (phytophaga or plantivores), carnivores, and omnivores assumes new 

 meaning, but at the same time must be carried further in order to 

 provide more definite pathways through the labyrinth of coactions. 



Choice of Food. With respect to the selection of food, it is helpful 

 to begin with the organism as it comes into free existence, whether 

 through hatching, birth, or transformation from other stages. Such 



