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posterior pairs confluent, or with some longitudinal confluence. 

 These frequencies are graphically shown in the following fre- 

 quency polygon : 



Fig. 52. Frequency polygon of the variation in elytral pattern of 905 speci- 

 mens of the flower beetle, Diabrotica soror, collected at Stanford University, 

 October, 1902. 



The similarity of the frequencies in these two lots of 905 in- 

 dividuals each, taken in the same locality at two times just one 

 year apart is striking. The variation in the species in this 

 locality is undoubtedly perfectly fairly shown by a series of 

 1,000 (app.). To test the value of a smaller series, in the first 

 lot (1901) the following frequencies of the characteristic varia- 

 tions were noted among the first 450 individuals (one half the 

 whole series) examined : 



Class A : 134 individuals. Class B : 15 individuals. Class 



