THE ORGANIZATION OF INSECT SOCIETIES 



429 



(Fyfe and Gay, 1938), that the control of 

 temperature is secondary to the control of 

 humidity, and that light unassociated with 

 temperature or humidity is not a factor 



Fig. 150. East face of the meridian nest of 

 the termite, Amitermes meridionalis, in north- 

 ern Australia. (Courtesy of G. F. Hill.) 



'^^ 



Fig. 151. South edges of se\eial nebts of 

 the meridian termite, Amitermes meridionalis, 

 in northern Australia. ( Courtesy of G. F. Hill. ) 



determining the behavior of blind termites. 



Sound signals are used by some of the 



social insects and doubtless are responsible 



for some coordinated activity. Some ants, 



notably Termitopone (Syntermitopone) 

 commiitata, stridulate sonorously during 

 their raids upon their termite prey. Soldier 

 termites belonging to widely separated 

 taxonomic groups hammer their heads on 

 the substrate when disturbed, often pro- 

 ducing a rapid tapping audible to the 

 human ear. Waves of tapping may be heard 

 moving through a colony. 



Probably the most important of the 

 senses used in colony integration is the 

 chemical sense. On occasion olfactory or- 

 gans may be separated from organs of taste, 

 but these chemical senses in insects are 

 often difficult to distinguish (Wheeler, 

 1928b, p. 231). 



Reactions to colony odor have been dem- 

 onstrated in everv group of social insects. 

 Strange odors initiate antagonistic responses 

 in most groups. The odor of an individual 

 may be easily modified experimentally. Not 

 onlv is it possible to initiate anta8;onism 

 to another individual in the same colony of 

 ants, termites, or bees by changine the odor 

 of the individual, but it is also possible to 

 introduce strange individuals into a colony 

 by givinsj them the colony odor. Individuals 

 from different colonies may be 8;iven similar 

 odors by keeping them in the same nest 

 for a few hours, but protected from each 

 other, by anesthetizine; all present with the 

 same gas, or by cooling them in a refrigera- 

 tor, and allowing them to recover together. 

 Droplcin (1941) was thus able to condition 

 different species and even different families 

 of termites to live together amicably. It 

 may be assumed that a neutral substance 

 on the surface of the insect absorbs the 

 odor of the environment and that in- 

 dividuals react antagonistically to any in- 

 sect that does not have the colony odor, 

 whether the insect is of the same or a 

 different species. Termitophilous beetles are 

 accepted or rejected by a termite colony 

 on the basis of their odor in much the 

 same manner that an individual termite 

 may be accepted or rejected. In addition 

 to the modifiable odor, there are probably 

 inherited odors that separate species. 



Subtle chemical differences may deter- 

 mine cannibalistic action common among 

 ants and termites. Cannibalism is often ini- 

 tiated by injury. One may even see that 

 the injured part attracts attacking individ- 

 uals. The parallel to phagocytosis within 

 the organism is fairly obvious. Canni- 



