Analysis of Heterogeneity in the Population 279 



The first conditions in this colony were determined from collections made at 

 random in the year 1903. The first census for this location shows at once a 

 decided difference from the condition prevailing in the Chapultepec colony. 

 Conspicuously isolated from the mass of the population is a group composed of 

 biotype 1, while 2 and 3 are wanting in this line of development in both the 

 sexes. The biotypes 10, 11, and 12 are also wanting in both sexes, and both 

 show 9 fairly well developed, while 5, 6, and 8 are poorly developed, if repre- 

 sented at all. The distribution in the population is uniform for the sexes. 





9 



31 ^ 



f * 12 



Sti 31 



. * ■" - ''ml 20 42 *#■■> fm^'--' 48 



24 :^-'*«:f 5J 51 ,^-m m^- « 



agi_- 9G 



i?^ ^ ^i^^ 42 



»3g: 



17 



/ •"'^■■■\^^ 4 



/ ^r^^ir " / \^" 



9 3 12 9 



342 Males. Total 857. 515 Females. 

 Fig. 66. — Census of first annual generation at Texcoco in 1903, showing condi- 

 tion of the pronotal pattern. 



7 ^^ 



6 ,-'it''-.„ „ viS^.. ..<W- 



14 .-«► \ ^^ 



11 -'-- iSfr /'m- 31 



31 -,-\^'.; ■&»-- 55 



12 -m 



i^--'^ 42 



7 -^-m]- I «*--- 51 



14 :-"i@« , ; Wy- — 86 



41 tjn^ if^-_^ 45 



19 ''■-'■i^ iiff..-; 92 :l^ ^^ : 92 



i«* ««*- 



/ W, fV=f:^ 39 



I m, ^ 41 / iiti-\ - ^,^ 14 



/ "" \ \ 



9' 17 8 '5 n 



418 Males. Total 903. 485 Females. 

 Fig. 67. — Census of second annual generation at Texcoco in 1903, showing con- 

 dition of the pronotal pattern. 



The second generation from this location of which the census was made 

 showed essentially the same condition in the population as was found in the 

 first yearly generation. These determinations are shown in figures 66 and 67. 



In the season of 1901: two censuses were taken ; the first showing in both sexes 

 considerable restriction of the range in the character, with the complete absence 

 of any isolated groups and no trace of the isolated biotype 1 group that was 

 found in the previous year. Biotypes 1, 2, and 3 were entirely wanting, as were 

 10, 11, and 12 in the males and 11 and 12 in the females. In both biotypes 5 

 and 6 were wanting or weak, but in both 8 was well developed in the population. 

 Compared with the corresponding generation of the Chapultepec colony this 

 population is strikingly different. 



