420 



POPULATIONS 



terns that have not evolved societies in the 

 strict sense (p. 687; Wheeler, 1921; 1928b, 

 p. 17). 



The organization within intraspecies 

 populations reaches its most diagrammatic 

 expression in the strictly social insects (p. 

 687), i.e., those that exhibit adult division 

 of labor in their societies (Isoptera and 

 certain Hymenoptera). We here examine 

 some of the factors that facilitate the 

 grouping of the individuals into such a so- 

 ciety. More extensive discussion, together 

 with details of social activities, will be 

 found in the works of Wheeler (1907, 

 1926, 1928a, 1928b), Hegh (1922), and 



greater eflBciency associated with speciali- 

 zation of function— and thus illustrate the 

 principle of division of labor characteristic 

 of all levels of biological integration (p. 

 683). 



A well-defined division of labor is 

 characteristic of the strictly social animals. 

 Separated functions of the parts make co- 

 ordination necessary. Division of labor and 

 integration advance as reciprocal manifes- 

 tations in both ontogeny and phylogeny of 

 the social population, paralleling similar 

 manifestations in the organism. This par- 

 allelism between the organism and the so- 

 ciety is included in the concept of the 



Fig. 146. The tliree primary castes of the termite, Syntermes snyderi, from British Guiana; A, 

 winged reproductives; B, mandibulate soldiers; C, workers. 



Emerson (1938, 1939, 1939a, 1942, 1943, 

 1947). An examination of the division of 

 labor between individuals composing the 

 group and the integrative mechanisms that 

 give unity to the group should afford a 

 perspective both for an understanding of 

 aggregations in general and for the analo- 

 gous human society of which we are a part. 



DIVISION OF LABOR AMONG 

 SOCIAL INSECTS 



A self-sustaining biological unit must 

 acquire the energy for life from the envi- 

 ronment, protect this energy from exploita- 

 tion by other organisms, maintain ecologi- 

 cal position, and reproduce its kind. The 

 fundamental adaptations for these biologi- 

 cal necessities are somewhat separated in 

 the organism— probably because of the 



supra-organism (pp. 427, 435, 693, 698). 



The reproductive castes function for the 

 maintenance of the species and for the 

 founding of new colonies. In becoming 

 specialized for reproduction, enlargement 

 of the gonads in the queens is accompanied 

 by speciahzed sexual behavior and regres- 

 sion of feeding and protective adaptations. 

 The reproductive castes may thus be anal- 

 ogized with the gametes of the organism, 

 which have also become specialized for 

 maintenance of the species and do not 

 develop the functions of the somatic cells. 



In the more primitive social Hymenop- 

 tera (wasps, bees, and ponerine ants), the 

 worker caste is the only sterile caste and is 

 always female. In the termites, the worker 

 (Fig. 146) is found only among the more 

 specialized families and may be either a 



