Analysis of Heterogeneity in the Population 



283 



colony, there was a wide range in the character of the population with no well- 

 developed isolated groups, but in the Texcoco colony the sharp restrictions of 

 the central mass of the population and the evident propensity to produce widely 

 and sharply isolated groups would seem to indicate for the two a different condi- 

 tion either in the population, in the medium, or both. Comparison of the condi- 

 tions in the two locations on the basis of the climatic data that I can give is not 

 satisfactory. In the latter part of the season of 1906 the conditions as regards 



14 ;^<: 



42 ^00. 



6 14 9 



/ / 



36 - 

 31- 

 29- 

 36- 

 19- 

 42- 



"l?!!^- 





1 1 1 



iMi^— 12 



CS?— 31 

 ^, —42 



m- 51 



\S^ IM 104 



Ifcl* «*► 98 



i»iM« i^ 95 



•itji ^^ 46 



12 



55 



31 



42 



34- — 



26 



25 — 



5 18 12 



( 



' <*- 



/ Mf^ 



! :«— 51 



^wF/ '0 — 5e 



-m «Bf..-- — 61 



■ , ^' 77 



^ rm- 86 



^m m 58 



77 



75 



/ / 

 1 3 



'm-x 



j /,«* ^ 

 I !.... \ 



I 



^\ 



\ 



7 14 9 



11 9 



\ ^^^ 



13 ' ' 



876 Males. Total 1874. 998 Females. 



piQ_ 74. — Census of first annual generation at Texcoco in 1907, showing sudden 

 marked extension of pronotal pattern in the array in all directions. 



m~7 



21 — 



— r®\ ,'^^ 11 



'-m^'^\. 46 



*'^ *^-> -92 



i\m^,^'T-- — 61 



14 



378 Males. Total 747. 369 Females. 



Fig. 75. — Census of second annual generation at Texcoco in 1907, showing 

 reduction of the general mass of the population as far as pronotal pattern Is 

 concerned and increased number of Isolated groups. 



the precipitation and its distribution were more uniform and propitious to the 

 development of this species than common, a fact that is partly indicated on the 

 climatic record by the high rainfall in the latter portion of the season, which 

 was also well distributed. The somewhat lower temperatuxes in this portion 

 of the season acted perhaps to check or counteract the opportunity presented by 

 the precipitation for the population to show wider ranges than common, which it 

 did not do. 



