494 PROCEEDINGS OF THE AMERICAN ACADEMY. 



the soldiers of Pheidole are seen in the field, and when they are, they 

 are usually idle. 



3. It was found in Camponotus americanus and I have no reason to 

 doubt it is likewise true of the other species of this genus and of the 

 species of Pheidole which I studied, and, indeed, for ants in general) that 

 a few individuals were much more active than the others, not only in 

 foraging, as was proved by Lubbock ( '82) for certain species, but also 

 in building and in tending the young ; and these more active ants 

 were not all of the same size. Moreover, some of them were about 

 equally concerned in more than one activity. This is probably due 

 to such individual psychical differences as those to which Escherich 

 ( : 06, p. 45) refers, and is in agreement with the statement of Fielde 

 ( : 03^, p. 621) that "a few individuals among ants do most of the 

 work undertaken." 



4. In both Camponotus and Pheidole, there were many more ants in 

 the colony than were active at any one time. This was true not only 

 in artificial nests, but also, though to a less extent, in the field. Lub- 

 bock ('82) found this limitation of activity to be very striking in his 

 artificial nests of i^(9rw2/ca /M5ca and Polyergus containing ^^the usual 

 slaves" though the numbers of ants in his colonies were much smaller 

 than those in mine. The artificial conditions, which were unavoidable 

 in such nests as either of us have used, must evidently be responsible 

 for the very small number of ants which were active under these cir- 

 cumstances, as compared with the conditions out of doors. But the 

 proportion of active ants in my colonies w^as much larger than in his. 

 Although it was found that the proportion of individuals which were 

 active in natural nests was much greater than in the artificial nests of 

 the laboratory, nevertheless, when compared with the size of the whole 

 colony, the number is surprisingly small even in the natural nests. In 

 Camponotus it is, to judge from my own observations, somewhat smaller 

 than in Pheidole. 



It was also found that the number of individuals which are active in 

 a colony is not closely correlated with the whole number in the colony, 

 for often more ants are found to be active in a very suall colony than 

 in one slightly larger. It is certain, however, that if a very large and 

 a very small colony are compared, the large colony will be found to 

 have many more individuals at work than the small one. 



5. In regard to the kind of work done by individuals at different 

 ages, it may be said that my studies on C. herculeanus pictus confirm the 

 statements of Forel ('74, p. 262), Per^z (:00, p. 769), Wheeler (:07^ 

 p. 87), and others, that ants when they emerge from the pupal state 

 attend especially to nursing and somewhat to other duties within the 



