430 



POPULATIONS 



balism is increased among termites at 

 periods when nitrogenous material is defi- 

 cient (Cook and Scott, 1933). Cannibalism 

 at times probably regulates the colony 

 population much as phagocytosis regulates 

 some aspects of the cell population within 

 an organism, and may consequently be 

 considered adaptive behavior. 



The adaptive drone-elimination behavior 

 of honeybee workers (p. 690) is probably 

 initiated by odor stimuli, although the de- 

 tails of the mechanism are unknown. Drone 

 elimination is the most remarkable case of 

 population control known among the social 

 insects. 



Pardi (1948) gives an interesting account 

 of social dominance and a social hierarchy 

 among the several overwintering females of 

 the wasp, Polistes ^alliens. In Italy these 

 are associated with the founding of a colony 

 in the spring. Farther north, the colony is 

 usually founded by a single female. 



In the "polygynic" Italian colonies, one 

 of the females remains on the nest, lays 

 eggs, is less active in construction work, 

 and dominates her associates. The domi- 

 nated females are more active in bringing in 

 food and building the nest, but lay fewer 

 eggs. The ovaries of these "auxiliary 

 females" gradually decrease in size and 

 function. After the workers appear, the 

 auxiliary females are eliminated by the sting 

 of the dominant female (queen) or by ex- 

 clusion from the colony. The dominance- 

 subordination relations establish an order 

 for the division of labor and thus benefit the 

 group if not too severe. 



In the contacts among the females and 

 also between females and workers, and 

 among the workers, the dominant individual 

 repeatedly strikes the head of the other 

 with her antennae, and the subordinate in- 

 dividual takes a characteristic position 

 (akynesis) with head lowered. During the 

 first contact, the dominant individual gives 

 liquid to the subordinate. Later the sub- 

 ordinate regurgitates liquid that mav be 

 sucked by the dominant. The subordinate 

 gives more liquid to the dominant than it 

 receives. 



The dominant generallv maintains its 

 position with the same individual in later 

 contacts until dominance is lost with age. 

 Fighting; often occurs during the establish- 

 ment of the order. Sometimes individuals 

 are equal and are intolerant of each other. 



A linear hierarchy is often established not 

 unlike the hierarchy of hens (see p. 413). 

 Triangles occur in some cases. Males are 

 dominated by both females and workers. 

 If the queen is eliminated, the next lower 

 female takes her place, and her ovaries in- 

 crease in size and function. Workers can 

 take the place of the queen and can rapidly 

 develop egg-laying capacity. There is a 

 close correlation between dominance and 

 size of ovary. 



Although hierarchical relations may in- 

 fluence the social system of primitive social 

 insects, there is little to indicate much im- 

 portance of such relations in the more 

 advanced insect societies. Possibly the more 

 cooperative types of integration replace the 

 social hierarchy based upon individual com- 

 petition as the societal system advances 

 during development and evolution. In this 

 connection it should be pointed out that a 

 social hierarchy resulting from individual 

 combat depends upon a capacity to learn, 

 and the establishment of social order of 

 such a type would be expected to be much 

 more characteristic of vertebrate animals 

 than of insects. 



Wheeler (1918) proposed the concept of 

 trophallaxis (exchange of nourishment) as 

 a mechanism of integration among the 

 social insects. Olfactory as well as gustatory 

 exchanges are included in the concept 

 (Wheeler, 1928b, p. 231), and the theory 

 may also be expanded to include tactile 

 stimuli (Schneirla, 1946). Many larvae as 

 well as adults have glandular secretions 

 that induce social activity. These glands 

 may be generally distributed over the sur- 

 face of the body or may be localized in the 

 so-called exudatoria. Direct feeding by 

 glandular secretions, like the royal jelly se- 

 creted from the pharyngeal glands by the 

 worker honeybee, may occur. In most 

 instances the secretions have special, at- 

 tractive qualities that induce licking and 

 grooming. Such secretions may carry 

 physiologic agents that influence growth as 

 well as induce behavior reactions (p. 428). 

 The fact that other participants in the 

 trophallactic circle, such as the termito- 

 philes and mvrmecophiles, convergently 

 develop specialized glandular secretions 

 that seem to enable them to adjust to the 

 social systems of their hosts is proof of the 

 importance of these chemical substances for 

 social integration (see pp. 719-721). 



