432 PROCEEDINGS OF THE AMERICAN ACADEMY. 



letically. It is furthermore probable that, since the large workers 

 more closely resemble the queen, they are more primitive than the 

 small ones. Emery, then, classifies ants according to the condition 

 of the workers as follows : 



I. Ants with only large workers. 



II. Ants with large and small workers. 



a. The extremes connected by intermediate forms. 



b. The large and small workers without intermediate forms. 



III. Ants with only small workers, which are very different from 

 the queen ; due to dropping out of large workers. 



IV. Ants with one kind of workers, which are smaller than the 

 queen through increase of size of queen. 



V. Ants from which have disappeared the worker class because of 

 parasitism. 



According to this classification, only the species which fall within 

 the second group offer more than one form of workers in the same 

 species. Hence, I have chosen as examples of workers with extremes 

 connected by intermediate forms, two species of Camponotus (C. ameri- 

 canus and C. hercideanus pieties). As the only available species in 

 this region of the country which falls under the division " large and 

 small workers without intermediate forms " is Fheidole jnlifera, I have 

 also selected that species. In addition, I succeeded in collecting 

 P. vinelandica from New Jersey, and in obtaining P. dentata through 

 the kindness of Mr. Carl Hartman of Austin, Texas. 



B . Polymorphism of the Species Studied for Division of Labor. 



1. Camponotus. — In Camponotus the workers form a continuous 

 series from the smallest, which have heads much longer than broad, 

 to the largest, whose heads are nearly as broad as long. This was 

 established for Camponotus americanus by measuring nearly 500 in- 

 dividuals, most of which were alive. To secure significant and reliable 

 results requires the selection of suitable and easily identified points on 

 the head and careful attention to the position of the parts during 

 measurements. In using the microscope to view the head and to get 

 the distance between points in its outline it is especially necessary to 

 have the heads of the individuals which are to be compared with one 

 another held in the same relative position. It was found practicable 

 to do this by pressing the head firmly into a small mass of rather soft 

 bees' wax mounted on a glass slide. Usually the wax thus employed 

 held the head in the desired position, but sometimes it was found 

 necessary to push the fore feet of the animal also into the wax to 

 prevent the ant from pulling its head away. The aim in orienting the 



