296 



The Mechanism of Evolution in Leptinotaesa 



the Chapultepec colony, which went into hibernation with the native population 

 and passed the cold, dry season in the new location. The purpose of the intro- 

 duction was to discover, if possible, whether the condition of the population &s 

 shown in the censuses was the result of the conditions of the environment or the 

 constitution of the materials, which in some unknown manner had become 

 limited to the narrow range of heterogeneity shown. It might be expected from 

 the result of the introduction that the condition of the population would change 

 in its nature, or that the new introduced conditions would be obliterated. 



11- 



19—^ 

 31- 







— 11 



14 



71 



— •74 



— -86 



— -92 

 ---71 



15 

 506 Males. 



Total 1062. 



14 11 



556 Females. 



Fig. 96. — Census of first annual generation at Chalcicomula In 1908, showing 

 return of the population to the condition observed most frequently In the location. 



■m 



-17 



19 



31 



25 -' 





fe^ 155 



\ 

 \ 



401 Males. Total 896. 



12 19 

 495 Females. 



Fig. 97. — Census of second annual generation at Chalcicomula in 1908, showing 

 presence of isolated groups of biotypes 1, 10, 9 and 7, after the introduction of the 

 heterozygous mass from the outside. The population in general is closely massed 

 around biotype 7 as in previous instances. 



I do not know how many survived the cold, dry winter in this location, but 

 when I saw the product of the native population and the introduced materials 

 in the first summer generation in 1908 there was little trace of the introduced 

 materials, with the exception of an isolated group of females of biotype 12, as is 

 shown in the record in figure 96. The second census of the season showed the 

 same imiform population, but present in it were divergent isolated groups of 

 biotype 1 in both sexes, 6 and 12 in the males, and extreme 8 in the females. 

 These groups were strong in proportion to the population (fig. 97). 



