434 



POPULATIONS 



male following in tandem. The tandem be- 

 havior results from the symmetrical tactile 

 stimulation of the eighth, ninth, or tenth 

 antennal articles of the male. Abnormal be- 

 havior always occurs in experiments in 

 which less than eight articles are left in 

 one antenna, and sometimes occurs with the 

 removal of the eighth, ninth, or tenth arti- 

 cle. Experimental removal of a portion of 

 the left antenna behind the eighth article 

 results in the male moving forward to the 

 head of the female on her right side. This 

 behavior of the male may also occur with 

 experimental removal of the eighth, ninth, 

 or tenth article. He moves forward on her 

 left side if the right antenna is removed be- 

 hind the eighth article, and this action 

 sometimes happens if the eighth, ninth, or 

 tenth article is removed. Removal of the 

 peripheral portion of either or both anten- 

 nae beyond the tenth of the seventeen or 

 eighteen articles in the complete antenna 

 does not modify tandem behavior. Removal 

 of both antennae behind the eighth article 

 always destroys the tandem response. 



The sensory stimulus that seems to deter- 

 mine whether the queen bee will lay a 

 fertilized egg that develops into a worker, 

 or an unfertilized egg that develops into a 

 drone, is the slightly different thickness of 

 the side walls of the drone and worker 

 brood cells constructed by the workers. The 

 walls are 0.076 to 0.092 mm. thick in 

 worker cells, and 0.127 to 0.152 mm. thick 

 in drone cells. One may guess that this 

 difference in thickness stimulates the closing 

 or opening of the spermathecal duct through 

 which the spermatozoa pass to the vagina, 

 where the egg may be penetrated by a 

 sperm cell (Flanders, 1939). 



The action of army ants in using their 

 own bodies in the construction of smooth 

 and level roadways and of their bivouac 

 (Fig. 152) is also probably a reaction to 

 tactile and kinesthetic sensations. 



The geometrical precision and obvious 

 sensitivity to subtle spatial factors and 

 subtle stresses and strains in the walls of the 

 abodes of the social insects are extraordinary 

 and indicate complex group behavior, the 

 mechanisms of which are almost wholly un- 

 known. Species specificity of the nest pat- 

 terns (Figs. 231-233) and the construction 

 by sterile workers that have no way of learn- 

 ing from previous generations of workers, 

 indicate that nest construction by the social 



insects is genetically determined in almost 

 all cases, and thus illustrates remarkable in- 

 stinctive group and social behavior. 



The architecture of the social insects 

 shows many spatial and geometrical rela- 

 tions that would seem to be explicable only 

 through tactile and kinesthetic senses 

 (Emerson, 1938). Such aspects as the size 



Fig. 154. Nest of the termite, Procubitermes 

 niapuensis, with chevron-shaped rain-shedding 

 ridges on the trunk of a tree in the rain for- 

 est of the Belgian Congo. (Photograph by 

 Herbert Lang.) 



of the nest cells or chambers, the horizontal 

 shape of the chambers, the layering of the 

 tiers of cells, the supporting pillars of the 

 chambers, the replication of ventilation 

 pores (p. 633), the radial symmetry of the 

 "mushroom-shaped" nests of Ctihitermes 

 having a rain-shedding cap, the bilateral 

 chevron-shaped rain-deflecting ridges on 

 the tree trunks above the nests of Con- 

 strictotermes cavifrons (page 645 and 

 Figure 235) and Procubitermes niapuensis 



