Analysis of Heterogeneity in the Population 273 



appeared in full strength, while 5 and 6 were still practically absent. This 

 generation was the product of the first, but under conditions that were unusual 

 for the place, in that the rains had been light in the earlier portion of the 

 season, the ranges in the humidity had been large, and the desiccation high, 



863 Males. Total 1897. 1034 Females. 



Fio. 56. — Census of first annual generation at the Chapultepec colony in 190S, 

 showing conditions in the population with respect to pronotal pattern and reia- 

 tlY* frequency of each type. 



210 "^^ipl .m 



214 :^0\ 4,: 



\ Wl. 42 / \ 



\^W^ 9 17 i4 



1624 Males. Total 3253. 1629 Females. 



)Fio. 57. — Census of second annual generation in the Chapultepec colony in 1905, 

 showing the array in the pronotal pattern, and a sudden change in aspect of the 

 population from that shown in preceding censuses. 



while in the latter portion of the season the rains had been copious and well 

 distributed, with low ranges in the desiccation and moderate and uniform tem- 

 peratures. The comparison of the two censuses of this season with those of 

 previous years shows different responses in the population to the conditions of 



