288 The Mecha^jism of Evolution in Leptinotaesa 



tribution of precipitation, temperature, and other factors the climatic complex 

 was such as to indicate optimum conditions, basing the estimate of the condi- 

 tions upon the conditions that had been found to be optimum in other locations. 

 In the Tlalnepantla habitat, however, no response to the conditions was mani- 

 fested in the population, such as had been observed in other locations. 



In 1905 the first generation in the location showed some change, but no iso- 

 lated groups, the area of the distribution of the pattern being " continuous," but 

 showing development along the direction of the biotypes 3 and 4, also in the 

 direction of 9 and 11. Biotypes 5, 6, and 8 were feebly represented in both 

 sexes. In the second generation of this year the census showed the same con- 



9 — - 



31 M-'s^i 



n—M§j^ 



t- — "^ '^> — 21 •21—-^;:^ ^^^ — 47 



47 - -_^^ ^^ 5j ^_jig(jj^_^ 83 



''f^if^m V^ 96 m m 77 



/ / / ^^ ^ 39 7 m- ^r- 56 



/ / / \ / \ m^^ 39 



.8 17_?5. 9 22 n 



553 Males. Total 1072. 519 Females. 



Fig. 82. — Census of first annual generation at Tlalnepantla in 1905, showing 

 condition of the pronotal pattern. 



12 



-14 11. 



--^ 17 



m —21 ,, ,j^% ^^:^m---2i 



41— jfc %»=. ^1 34 j_p ^ 



46--^^.^ W -45 ^^ — ^ ^ m 38 



61 -:^tK|gi^ ^ ___.^g 46 -^ ^ _..3j 



49 .^ ^ ^^ _g2 49- -^ m *«► 42 



/ X <V7 ^ 26 / \ -V? 29 



/ \ / \ ^ -36 



14 31 19 z2 



665 Males. Total 1314. 649 Females. 



Fio. 83. — Census of second annual generation at Tlalnepantla in 1905, showing 

 an Increased array in pronotal pattern. 



ditions as in the previous generations. None of the isolated groups that were 

 so characteristic of other locations was found, and the poor development of the 

 more divergent biotypes in the population is characteristic of the location. Bio- 

 types 3 and 4 were fairly well developed, as was 5 in the males, otherwise the 

 census showed nothing of interest. The record of the censuses of these two 

 generations are shown in figures 82 and 83. 



The year 1906 showed in the location the first indication of any of the diver- 

 gent groups, there appearing in the males biotype 1, which were found in freshly 

 emerging condition, showing that they were a portion of the population, but 



