242 



The Mechanism of Evolution in Leptinotarsa 



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Fio. 35. — Showing the 12 biotypic groups Into which it has been possible to 

 separate the pronotum pattern of L. multitmniata. These groups are based upon 

 the fact that each has been isolated from the general population and reared in pure 

 homozygous acting pure lines through several generations in each, and represent 

 with present methods all the stable groups of the pattern as a whole that I have 

 been able to isolate. 



Fig. 36. — Showing arrangement of 

 the 12 biotypic groups into a general 

 scheme for the population as a whole 

 and different directions of combina- 

 tion and variation within the pattern 

 as presented by the population. This 

 schematic base showing the position 

 of the 12 biotypes within the popula- 

 tion has been used as the basis for 

 recording the heterogeneous condi- 

 tions found within the population of 

 this species in nature. 



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