THE ORGANIZATION OF INSECT SOCIETIES 



421 



sterile male or female. Among the primitive 

 termites, nymphs of the other castes per- 

 form the functions of the workers, which 

 are primarily nutritive and collect food 

 from the habitat (trophoporic field). In a 

 few instances the worker termites and ants 

 cultivate gardens of fungi (pp. 713, 714) 

 or, among certain ants, tend animals such 

 as aphids or coccids (p. 719) that may 

 be guarded and enclosed within shelters. 

 Food may be stored by the workers, either 

 in portions of the nest or in their own 

 bodies ("repletes" of honey ants). The 

 workers feed the other castes and young, 

 either with the gathered food or with 

 digested foods or secretions. Shelters rang- 

 ing from simple burrows to elaborate con- 

 structions are built by the workers. 



largest form of a polymorphic series) re- 

 main in the ground nests unless disturbed; 

 they then emerge in great numbers for the 

 defense of the colony. Their function seems 

 to be wholly protective. In some ants with 

 a sharp morphological difference between 

 the soldier and worker (i.e., Pheidole), ex- 

 perimental colonies composed of reproduc- 

 tives, larvae, and soldiers, without workers, 

 are maintained in a healthy state by the 

 soldiers (Gregg, 1942). 



REPRODUCTION IN SOCIAL INSECTS 



The reproductive castes of social insects 

 are least modified in comparison with their 

 solitary ancestors. A wasp queen is known 

 to have laid ten eggs in twenty-four hours, 

 and mature queens of primitive bees, ants, 



Fig. 147. Side \iew of army ants (Eciton hamatum) transporting their larvae slung under 

 their bodies during a change of the bivouac site. A large white-headed "soldier" stands guard 

 beside the trail in the upper left. (Photograph by Ralph Buchsbaum. ) 



Soldiers are primarily the protective 

 caste. The soldier is the primitive sterile 

 caste among the termites (Fig. 146), may 

 be either a male or female, and in the final 

 ontogenetic stage functions wholly for the 

 protection of the colony against predaceous 

 enemies. Soldiers are absent from the bee 

 and wasp societies, in which the worker de- 

 fends the colony in addition to its other 

 functions. Among the ants, the soldier is 

 always a sterile female, and shows many 

 intergradations of structure and behavior 

 with the worker caste. The army ant (Eci- 

 ton) "soldier" is the largest form of a 

 polymorphic series of workers (Fig. 147). 

 It captures and transports the prey, as well 

 as defends the colony with its sting and 

 large mandibles. The smaller army ant 

 workers also defend the colony with their 

 stings and smaller mandibles. In the leaf- 

 cutting ants (Atta), the soldiers (also the 



and termites often do not have greater 

 fecundity. The female in the more highly 

 social forms has increased her egg-l^yirig 

 capacity and often shows an enlarged ab- 

 domen commensurate with her enlarged 

 ovaries. Army ant queens periodically pro- 

 duce as many as 20,000 eggs in a few days. 

 A honeybee queen is known to have laid 

 3021 eggs in a day. A queen of a large ter- 

 mite colony (Fig. 148) may lay 6000 to 

 7000 eggs within twenty-four hours, and 

 she keeps up this rate without diel or sea- 

 sonal periodicities for many years (esti- 

 mated as long as fifty years). Having re- 

 linquished feeding and protective behavior, 

 as well as the care of her eggs and oflF- 

 spring, she is in eflFect a specialized egg- 

 laying machine. She has exudate glands 

 that are partially responsible for the feeding 

 and grooming bestowed upon her by the 

 workers. Great fecundity of queens is cor- 



