DAILY RHYTHMS IN SOCIAL ACTIVITIES 
OF THE HARVESTER ANT, POGONOMYRMEX BA DIGS* 
By Deborah M. Gordon 
Department of Zoology, 
Duke University, 
Durham, N.C. 27706 
Daily cycles in behavior are well known throughout the animal 
kingdom. There is some evidence that the activities of ant colonies 
are temporally organized so that, at a given time of day, a certain set 
of tasks is done. This study explores that possibility by examining 
temporal patterns in the social behavior of the harvester ant, 
Pogonomyrmex hadius. Such patterns should be distinguished from 
circadian rhythms to which conform endogenous, physiological 
events exhibited by individual animals (e.g. McCluskey 1958 and 
1965). The present study is concerned with daily rhythms in social 
activities performed by groups of ants. Two questions are ad- 
dressed: 1) Are certain tasks performed at characteristic times of 
day? 2) How do activity rhythms vary among different colonies? 
There have been many studies of daily temporal patterns in the 
overall activity levels of ant colonies, measured as the numbers of 
ants entering or leaving the nest (Levieux and Diomande 1978a, 
Hunt 1974, Hansen 1978, Van Pelt 1966), or the numbers of ants in 
certain areas for specified durations (Janzen 1967, Levieux and 
Diomande 1978b, Levieux 1979a and 1979b, Golley and Gentry 
1964). Temporal patterns of overall activity level are well docu- 
mented for several Pogonomyrmex species (Holldobler 1970 and 
1976a, Whitford and Ettershank 1975, Whitford et aL 1976). Some 
authors have described temporal patterns of selected social activities 
of various ant species (Moglich and Alpert 1979, Janzen 1967, 
Levieux and Diomande 1978a and 1978b), including Pogonomyr- 
mex (Willard and Crowell 1965, Holldobler 1976b). But, except for 
Holldobler’s (1976b) study of mating activity, the cited work pre- 
sents no systematic data on temporal patterns in behavior other 
than entering and leaving the nest. In some recent field studies of 
* Manuscript received by the editor November 21, 1983 
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