252 



KELLOGG AND BELL 



size of the wings while differences in measurements C and D 

 enable us to see if the variation in length of certain vein parts 

 (as between cross veins, points of branching, etc.), are directly 

 proportional to the wing size or have an independent variation 

 of their own. The polygons showing the range and mode of 

 the variation for each of these form dimensions are as follows : 

 Polygon of length left wing, fig. 37 ; polygon of length right 

 wing, fig. 38 ; polygon of width left wing, fig. 39 ; polygon of 

 width right wing, fig. 40 ; polygon of meas. C left wing, fig. 

 41 ; polygon of meas. C right wing, fig. 42 ; pol3'gon of meas. 

 D left wing, fig. 43 ; polygon of meas. D right wing, fig. 44. 



Fig. 44. Frequency polygon of the variation in measurement D (see fig. 34) 

 of right fore wings of 198 male black ants, collected at one time in one place ; 

 mean 20.2 micrometer units ; index of variability 1.33; coefficient of variation 

 6.58. 



Determining for the sake of fair comparison the coefficients 

 of variation for each of the form dimensions measured we find 

 them to be the following: Length, for left wing 3, right wing 

 4; width, left wing 4.4, right wing 4.22 ; meas. C, left wing 

 8.4, right wing 8.5 ; meas. D left wing 6.87, right wing 6.58. 

 Thus it is obvious that the variation in the vein parts, /. c, the 

 character or arrangement of the venation, is markedly larger 



