LIFE HISTORY OF CARPENTER ANT. I9I 



problem of polymorphism among ants in general a problem on 

 which much has been done and much written, but which I think, 

 has not hitherto been examined from this standpoint. 



The form of polymorphism we find here is what Eschreich in 

 his "Die Ameise " calls incomplete polymorphism. That is, 

 there is no distinct soldier-type, and there is a regular gradation 

 in the size of the workers from the very largest to the smallest, 



Fig. 3. Workers of C. pennsylvanicus arranged according to size and division of 

 labor. 



as shown in Fig. 3. I have grouped the twelve sizes shown in 

 this figure into four subgroups to which I shall refer as Nos. 1, 

 2, 3 and 4, as indicated in the figure. This division into groups, 

 I shall attempt to show later, is in harmony with an incomplete 

 division of labor that exists among the workers. 



The point revealed by a study of the life-history of a colony 

 that I think is of importance is the fact that these different sizes 

 of workers, and finally the winged forms, are produced at rather 

 definite periods during the life of the colony. This is shown in 

 Tables V. and VI. 



The colonies represented in these tables were all killed in 

 cyanide bottles and were then divided as accurately as possible 

 into groups according to the four sizes represented in Fig. 3. 



In all the colonies represented in Tables I. and II. every one 

 of the workers was of size No. 4, and in the smaller colonies of 

 Tables V. and VI., which, according to our previous conclusion, 

 were two years old, this size still very largely predominated. In 

 this latter group of colonies were found, however, a small num- 

 ber of size No. 3, and a still smaller number of No. 2, but not a 

 single No. 1. From this point on, so far as the tables go, all 

 sizes were found in all the colonies, and with the exception of 

 colony 6, Table IV., not any perceptible increase is shown in the 

 per cent, of the largest sized workers as the colony increased in 



