STUDIES OF VARIATION IN INSECTS 277 



C: 33 individuals. Class D: 228 individuals. Classes E, F 

 and G : 30 individuals. Class H : 10 individuals. 



Comparing this half series of the 1901 individuals with the 

 whole series the percentages of the frequencies of the different 

 variations are as follows : 



Class A : 34.5 per cent, in series of 906, 30 per cent, in series 

 of 450. Class B : 3.5 per cent in series of 906, 3.35 per cent, 

 in series of 450. Class C : 6.6 per cent, in series of 906, 7.35 

 per cent, in series of 450. Class D: 43.7 per cent, in series 

 of 906, 50.6 per cent, in series of 450. Classes E, F and G : 

 8.4 per cent, in series of 906, 7 per cent, in series of 450. 

 Class H : 3 per cent, in series of 906, 2.25 per cent, in series 

 of 450. 



The 1902 series of 905 (app.) individuals is composed of two 

 lots collected in same place, one of about 600 individuals taken 

 October 7, and the other of about 300 individuals taken October 

 15. Each of these lots classified separately reveals the fre- 

 quencies of the characteristic variations in nearly identical pro- 

 portions. 



From these examinations of short series there seems to be 

 little doubt that a series of 500 (app.) individuals of Diabrotica 

 soror from any locality contains all of the principal variations 

 in the color pattern in proportions representing the actual con- 

 ditions in the species as it exists in the given locality. 



An inspection of the frequency polygons for the series of 

 1901 and 1902 shows that the color pattern condition accepted 

 by entomologists (on a basis of the original description of the 

 species and repeated references to the pattern in the literature 

 of coleopterology) as diagnostic of the species is only one of two 

 modal color pattern conditions and is indeed the less frequent 

 one of the two. There are more flower Diahroticas with four 

 distinct black spots and a central transverse band (made by the 

 confluence of a pair of spots) on each elytron than there are in- 

 dividuals with six distinct spots on each elytron. Which is 

 soror? According to the views of the Pearson, Davenport, et 

 al.f school of variation students, thisbimodal frequency curve of 

 D. soror indicates a tendency toward the splitting of one species 

 into two, a beginning in the formation of a new species. In the 



