148 HUMAN BIOLOGY 



The larvae of many social insects (ants, wasps and ter- 

 mites) are not only fed by the adult members (parents and 

 workers) of the colony, but may in turn feed their nurses 

 with sahvary or other secretions. The young are therefore 

 a source of food for the adults and vice versa, and the ''fond- 

 ness" of the social insects for their young proves to be not 

 some altruistic "instinct," such as love or affection, but 

 the hunger of the individual and therefore an egoistic 

 appetite. There is also a trophallactic relation between the 

 adult members of the colony, which are constantly feeding 

 one another with regurgitated hquid foods (ants) or with 

 regurgitated semisoHd foods or feces or substances (exudates) 

 secreted from the surfaces of their own bodies (termites). 

 So powerful is this habit that it is extended even to many 

 of the heterogeneous insects which have managed to hve 

 in the nests of the social species, i.e. to the true guests 

 among the myrmecophiles, which hve with ants, and the 

 highly speciahzed guests of termites (termitophiles). Further- 

 more, since the senses of taste and smell are not differentiated 

 in insects as they are in the higher vertebrates, and since, 

 in the former, we may therefore more properly speak of a 

 single chemical sense, we are justified in including under 

 trophallaxis also an exchange of odors as one of the important 

 cohesive bonds in insect societies. There are, in fact, indi- 

 vidual, colonial and nest odors, which the social insects are 

 able to recognize and distinguish and therefore serve to 

 determine many of their reactions and much of their 

 behavior. Both the food and the odors thus constitute a 

 regulative, circulating social medium which not only func- 

 tions as a social cohesive, but in the case of the food, furthers 

 the growth and maintenance of the society in a manner 

 analogous to the circulating blood stream in the body of a 

 higher animal, which is also a society of cells. Of course, 

 the word "food" is here used in a general physiological 

 sense, both as nutriment and as a stimulant, or excitant, 

 because the amounts of the substances exchanged may be 

 extremely small though of such a chemical composition as to 

 produce pronounced reactions, just as a very small amount 

 of alcohol may produce much more violent reactions in 

 some people than large quantities of rice or potatoes. 



