272 



KELLOGG AND BELL 



(see p. 259) individuals classified on basis of variations in the 

 elytral pattern were examined and classified on basis of variations 

 in the pattern of the pronotum (dorsal aspect of the prothorax). 

 The modal pattern is formed by the presence of a pair of short 



FIG. 48. Diagram showing var. in prothoracic pattern of the convergent 

 lady bird, Hippodamia convergens. 



white diagonal lines or bars on the red-brown ground color of 

 the pronotum (fig. 48, A). These white lines may vary through 

 continuous gradations of shortening and lessening to total dis- 

 appearance, or may, while retaining their modal size, become 

 shaded or darkened by gradating steps until they are hardly 

 visible as distinct lines or spots at all. The frequencies of the 

 arbitrarily defined classes in this variation are as follows : 



Class A : 308 individuals with well-defined white bar-spots 

 (the mode) (fig. 48, A). Class B : 168 individuals with the 

 white bar-spots about one half as long and wide (= one half 

 size) as in Class A (fig. 48, J3). Class C : 31 individuals with 

 the white bar-spots about one third the size of those in Class 

 A (fig. 48, C). Class D : 13 individuals with with bar-spots 

 reduced to small subcircular spots or points (fig. 48, D). Class 

 E: i individual with bar-spots actually completely wanting 

 (fig. 48, F). Class F : 15 individuals with bar-spots clouded 

 (not white) giving effect of obliteration of marking (fig. 



48, -ff)- 



The frequency polygon for this variation is shown in fig. 49, 



in which Class F is not represented. 



