Analysis of Heterogeneity in the Population 281 



The second generation in this season showed still different conditions from 

 that of the first, in that there was an entire absence of biotypes 1, 2, and 3, in 

 both sexes; 10 was represented by a well-defined group that while small in num- 

 bers stood well apart from the population, and the female showed a weak develop- 

 ment of 13, while 8 was wanting in both, Biotypes 5 and 6 showed the same 

 general conditions that were found in the first generation of this year. Com- 

 parison of the findings in this generation of the population with that in the 



6 14 8 isiriil^ 8 



i2-«ft ! I ' 



m"w ~---^6 26 — i^^mil 



/m;^'i '-^i ^^42 



AX-*--- /// \ 



9 13 4 31 6 14 16 9. 



880 Males. Total 1478. 598 Females. 



Fio. 70. — Census of first annual generation at Texcoco in 1905, showing condi- 

 tion of the population with regard to the pronotal pattern and In this isolated 

 group. 



22 



40 



61 





^. , jm^—- 4 

 m>^c ^.:— -15. 



64 --"-*^' IM> 19 



«—^^- ""--_- Sflfli Hf. 81 



^lfr^'*t "''' 



/ / ^VV-^^^- 45 



ill \ \ \ 



11 4 12 I 19 6 



597 Males. Total 1006. 409 Females. 



Fig. 71. — Census of second annual generation at Texcoco In 1905, showing 

 reduction In the array presented by the population and the diminished number 

 in isolated groups. 



corresponding generation at Chapultepec still shows differences that are of con- 

 siderable magnitude, chief of which is the evident tendency in the Texcoco loca- 

 tion not to present so wide a range in the character in question, or the frequent 

 complete series in the different lines, and the greater frequency of groups iso- 

 lated by considerable gaps. The conditions of life on the whole were more severe 

 at the Texcoco location, with wider ranges in the temperature and desiccation 

 and more variable rainfall. Coupled vdth these conditions is the apparent dif- 

 ference in the population shown in the records. The findings for the two 

 censuses of 1905 are shown in figures 70 and 71. 

 19 



