434 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



anterior margin of the clypeus ; by " breadth " or " width " is meant 

 the distance between the lateral outlines of the head measured along 

 a line tangent to the posterior margin of the eyes. 



The first diagram (Figure 1) is a frequency polygon^ giving the results 



Ulh^ 



di 



Figure 3. 



Figure 4. 



of the measurements of width, Figure 2 that of length, Figure 3 that of 

 length multiplied by width, and Figure 4 the ratios found by dividing 

 width by length. In constructing the polygons the ants were divided 

 into classes. For the length a difference of 0.2 mm. was chosen as the 

 basis, the first class containing all individuals in which the length of 



