374 



The Mechanism of Evolution in Leptinotabsa 



the total complex in which they were existing. Figures 58 and 59 illustrate 

 well the condition in the population, and the fact that the observer who saw 

 only the 1905 generations would have continuity, and the one that observed the 

 populations of 1904 would have " mutations," and the stage would be set for a 

 fine series of pointless " brief communications." 



31 

 1655 Males. 



Total 3350. 1695 Females. 



Fio. 58. — Census of first annual generation at Cbapultepec colonT la lOOfl 

 ■bowing the array ot population In pronotal pattern. ' 



19 

 1842 Males. 



/ 



22 



1707 Females. 



Fio. 69. — Census of second annual generation at Cbapultepec colony In 1904, 

 showing the array In the pronotal pattern. 



The season of 1907 was in many respects an optimmn one, with the different 

 factors of the climatic complexes distributed in such fashion that they afforded 

 the best conditions for the growth of the population at all times and essentially 

 equal conditions in the early and late portions of the season, so that the condi- 

 tions in the population were unusually uniform throughout the season. 



The first census was made in the middle of July at the maximum of the first 

 summer generation, and showed full development of all the liaes, with the 

 exception of biotypes 5 and 6, which were not well represented, if present at 

 all. No isolated groupe were found, with the exception of the females where 



