THE ORGANIZATION OF INSECT SOCIETIES 



4lb 



10. The interdependence of organisms is 

 shown by the repeated observation that all 

 living things, from the simplest to the most 

 complex, live in communities. This is easily 

 seen in such microcosms as those of a pro- 

 tozoan culture dish, or a small lake, or in 

 biocoenoses, Uke those of an oyster bed. 



11. The evolution of truly social animals, 

 such as termites, bees, and ants on the 

 one hand and man on the other, has oc- 

 curred independently in widely separated 

 divisions of the animal kingdom. These 

 could hardly have arisen so many times and 

 from such diverse sources if a strong sub- 

 stratum of generalized natural proto-co- 



operation— call it physiological facilitatioii, 

 if you prefer— were not widespread among 

 animals in nature. Such tendencies precede 

 and condition the formation of animal con- 

 centrations, the existence of which is pre- 

 requisite for the development of group or- 

 ganization. 



12. No animal is solitary throughout its 

 whole life history. 



13. As in the individual organism, each 

 advance in complexity of the social hfe of 

 any group of animals is based on the de- 

 velopment of some means of closer coopera- 

 tion between the individual units of the 

 evolving group. 



24. THE ORGANIZATION OF INSECT SOCIETIES 



The social insects illustrate the culmination 

 of the action of various factors upon in- 

 vertebrate population groups (p. 393, Chap. 

 22). They have the general properties of 

 populations that have already been dis- 

 cussed at the beginning of this section 

 (Chapters 18-23): natality, mortality, dis- 

 persion, growth form, and density (p. 272). 

 The social insect colony, like other popula- 

 tions, resembles an organism in that it has 

 •structure, ontogeny, heredity, and integra- 

 tion, and forms a unit in an environment 

 (p. 683). 



Statistical and experimental analyses of 

 population factors have been appKed more 

 rigorously to infrasocial populations, par- 

 ticularly to laboratory populations. The so- 

 cial insects lend themselves to certain types 

 of quantitative analysis (p. 310; also see 

 Emerson, 1939a), as may be seen in the 

 studies by Talbot (1943, 1945), Boden- 

 heimer (1937), and Pickles (1935, 1936, 

 1937, 1938, 1940). 



The growth curve of a social insect 

 colony has been shown to be sigmoid or 

 logistic (Bodenheimer, 1937; see also Fig. 

 102). This results from factors influencing 

 the reproductive capacity of a few individ- 

 uals, or even of a single queen, together 

 with dispersion and mortality factors oper- 

 ating upon various stages in the life cycle, 

 upon sterile castes making up the bulk of 

 the adult population, and upon reproduc- 

 tive adults. In some respects the colony 

 population is comparable to populations of 

 infrasocial species (Fig. 101). In other 



respects, populations of colonies are com- 

 parable to populations of reproductive in- 

 dividuals of infrasocial species. 



Analysis of social populations may some- 

 times necessitate a further refinement of 

 methods usually adequate for infrasocial 

 groups. For example, Pickles (1938) 

 divides density of ant species into three 

 categories. Lowest density is the total 

 population divided by tlie area covered by 

 the census; economic density is the total 

 population divided by the territory actually 

 occupied; greatest density is the population 

 of the nest at night. Proportional relations 

 of such densities to weight of the ants per 

 unit area vary with species and conditions 

 and facihtate a more refined comparison 

 and interpretation (Emerson, 1939a). These 

 terms may also be applied to certain in- 

 frasocial populations. 



Many gradations of integration may be 

 found in various subsocial populations 

 (family systems and aggregations of 

 adults) that connect the social insects with 

 the various types of infrasocial groupings. 

 In some instances the subsocial species may 

 be considered a phylogenetic stage in the 

 evolution of the social insects (pp. 686 and 

 687). 



In other instances the subsocial popula- 

 tion is not ancestral to the strictly social 

 forms; nevertheless, it illustrates principles 

 of integration and division of labor that 

 logically connect the infrasocial and strictly 

 social. The beetles, in particular, offer 

 many examples of subsocial population sys- 



