560 



THE COMMUNITY 



comes progressively less arrhythmic and 

 more regular as the child becomes adjusted 

 to its routine of existence in its particular 

 habitat niche. This is an interesting parallel 

 to the induction of periodism in the grain 

 beetle, cited previously. 



Man's adaptability is well documented 

 (Freeman, 1935; Kleitman, 1939) in his 

 habituation to various types of work on a 

 periodic basis, and such periodism is paral- 

 leled physiologically by periodism in phos- 

 phate excretion, body temperature, tonicity 

 of skeletal musculature, energy output, 

 sleeping habits, and numerous individual 

 skills. Thus man is highly adaptable, capa- 



Diel environmental periodicity, then, is 

 in agreement with organismal or popula- 

 tional periodicity, just as environmental 

 stability is in agreement with organismal 

 or populational arrhythmicity. 



An interesting intermediate position be- 

 tween the two conditions conducive to 

 aperiodicity is exhibited by the beetle, 

 Passalus cornutus." The usual habitat niche 

 of this insect is the decaying log of the 

 forest floor. The moist, dark log interior has 

 a smaller range, and an appreciable lag in 

 temperature as contrasted to external con- 

 ditions (Graham, 1920, 1922, 1924, 1925, 



Hundreds 



Fig. 197. Diagram of four possible levels in the degree of periodicity or aperiodicity of man 

 with respect to the diel cycle of the inanimate environment. 



ble of working and resting without ref- 

 erence to the diel cycle. This is an interest- 

 ing parallel to the working habits of cer- 

 tain ants. 



Methods of transportation and of com- 

 munication are usually aperiodic wdth re- 

 spect to the diel cycle in the sense that they 

 may operate day and night, as are phases 

 of industry, property protection, entertain- 

 ment, and medical attention. The degree 

 of social arrhythmicity varies with the de- 

 gree of complexity of organization of man's 

 society. Thus the isolated farmhouse bio- 

 coenose usually is nearly as periodic as its 

 surroundings (Fig. 197); the country ham- 

 let is slightly less periodic; the small city 

 still less rhythmic; and the large metropoh- 

 tan areas are never inactive as a whole (O. 

 Park, 1941a). 



1939; Savely, 1939), as noted in Figure 

 198. 



In such relatively stable habitat niches 

 the passahd beetles are subsocial (Wheeler, 

 1923; Miller, 1932; Pearse, Patterson, 

 Rankin, and Wharton, 1936), and the adult 

 population has been shown to be arrhyth- 

 mic (O. Park, 1935, 1937). 



Thus, with respect to the diel cycle, al- 

 though many nonsocial, wood-dwelling ani- 

 mals are periodic, subsocial passahds are 

 aperiodic; and, although certain social ani- 

 mals such as certain ants, termites, and 



* The black, subsocial "bess-bug" so familiar 

 in logs in advanced stages of decay, and widely 

 known as Passalus cornutus Fabricius, has been 

 reviewed in a revision of the family, Passalidae, 

 by Hincks and Dibb (1935), and designated as 

 Popilius disjunctus Illiger. 



