BUCKINGHAM. — DIVISION OF LABOR AMONG ANTS. 



463 



have frequently seen the same ant occupied first in, one and then in 

 another activity. Indeed, some individuals were about equally con- 

 cerned in two or more activities. When, however, we consider all the 

 evidence on the various activities, we are warranted in the conclusion 

 that in fighting, the largest ants predominate ; in building, the small 

 and middle-sized ones ; in tending the young, the smaller individuals ; 

 and in foraging, all sizes except the largest. From field evidence on 

 Camponotus pictus I can corroborate these conclusions. 



And yet it is evident that certain 

 individuals, regardless of size, are much 

 more alert in each activity than others ; 

 this at first sight suggests a division 

 of labor not correlated with size differ- 

 ences. In Figure 19 individual ants, 

 arranged on the axis of abcissas in the 

 order of the size of the head, are desig- 

 nated by the letters of the alphabet ; 

 at the left the ordinates indicate the 

 per cents of the possible number of 

 times which each of these twenty-one 

 individuals {A-JJ) was engaged in the 

 several activities, these being plotted 

 as solid black lines. The upper curve 

 shows "building," the second, "tend- 

 ing the young," the third, " foraging," 

 and the fourth (bottom) is the sum of 

 the other three curves, which thus 

 gives the total activity of each indi- 

 vidual for these three occupations. 



The dotted curve shows the various head sizes in sq. mm. (length x 

 width), the values being indicated by the figures in the right margin. 

 It may be seen at a glance : (1) that there is no very obvious corre- 

 lation between any of the activities when compared with one another 

 (curves 1, 2, and 3) ; (2) that there is no close correlation between any 

 of the various activities and the size of the head (compare curves 1, 

 2, and 3 with the dotted curve) ; and (3) that certain individuals are 

 in general much more active than others (bottom curve). The fourth 

 curve shows that, on the whole, the smaller individuals are the more 

 active. While there is a slight preponderance of certain sizes (D = 2.30 

 sq. mm.) in certain activities (building), there is also an individual 

 diligence in several activities, and this seems to be more or less inde- 

 pendent of size. 



60 



50 



40 



30 



20 



10 



1.5 Z5 3.5 4.5 5.5 6.5 7.5 

 Figure 18. 



