298 The Mechanism of Evolution in Leptinotaesa 



there emerged in the spring a large number, and they interbred with the native 

 population and inter se, giving the resultant distribution of the population in 

 the first generation shown in figure 100. In this array the mass of the popula- 

 tion is still gathered about the same condition as in the other generations exam- 

 ined, and the development of the line composed of biotypes 1, 3, 3, and 4 is, rela- 

 tive to the entire population, weak and may well have been due to the inbreed- 

 ing of some of the Puebla immigrants, of which all of these conditions were 

 present in the population introduced, and not to the inbreeding of the native, 

 and introduced with the dominance of the introduced over the native. Census 

 methods could not decide this in nature. 



765 Males. Total 1629. 864 Females. 



Fig. 100. — Census of first annual generation at Chalcicomula in 1910, showing 

 array in population after the introduction of a large foreign population from 

 Puebla. 



I have no further records of the fate of the colony with its immigrants, owing 

 to the disturbed condition of the area in the seasons of 1911 and 1912. An 

 attempt to gain information of the condition of the colony in the winter of 1911- 

 12 by digging for the hibernating beetles also gave no results, owing to the 

 reluctance of the labor in town to go on a strange errand into the country. To 

 judge by past experiences in the location, it is probable that the introduced 

 material was progressively incorporated into the population, leaving its presence 

 indicated for longer or shorter periods by changed ranges in the character most 

 considered. 



THE PUEBLA COLONY. 



The location of this colony in the Eio Atoyac Valley, on the brink of the 

 Mexican Plateau, in a location open to the warm winds from the low, hot valleys 

 to the southward, and protected from the cold winds from the northern plateau 

 and high volcanoes, with higher rainfall distributed over a somewhat longer 

 portion of the year, gave the location a more favorable set of conditions than any 

 of those previously examined, with the exception of Chapultepec, whose peculiar 

 topographic situation gave it especial advantages over other locations in the 

 valley of Mexico. At Puebla two collections near the location chosen, made in 

 1903, gave data showing the difference that existed in that year between this 

 location and others examined, and in 1904 observations were begun and con- 

 tinued to the close of 1908, covering 10 generations in the location. 



