STUDIES OF VARIATION IN INSECTS 



227 



The frequency polygon showing graphically the variation in 

 length of 98 (202 individuals had the wing tips battered) right 

 fore wings in this lot of workers, and the frequency of the 

 various classes may be seen in fig. 16. 



The mean length is 214.3 (units of the micrometer), the mode 

 (most frequent length) 215 (units of the micrometer), the stan- 

 dard deviation 2.37 (units of the micrometer) and the coefficient 

 of variation i.i. The frequency curve follows fairly well for 

 such a short series the theoretical one of the law of error. 



The frequency polygon showing the variation in the breadth 

 of 296 wings is as follows : 



FIG. 17. 



The mean breadth is 50.7, the mode 50, the standard devia- 

 tion 1.3, and the coefficient of variation 2.57. Thus comparing 



