312 



The Mechanism of Evolution^ in Leptinotaesa 



41 83 



697 Males. 



Total 1535. 838 Females. 



Fig. 119. — First census at Tlerra Blanca in 1907 showing condition in the popu- 

 lation with regard to pronotal pattern. 



Fio. 120.— 

 Dotal pattern 



34 91 



438 Males. Total 1059. 



Second census at Tlerra Blanca in 1907, showing condition In pro- 



97 



-171 



-192 



44 13 51 7 



Total 1973. 1027 Females. 



Fia. 121. — First census at Tierra Blanca In 1908, showing sudden Increase In 

 certain directions in pronotal pattern and the sudden rise of three strongly 

 developed isolated biotypic groups in both sexes. 



41 ^y 3g ^ 



«zz:^ 41---- 



SSte^ ^m^m^ ^^^ .«^ ^*^T»- -114 



7^ ^^fr — ^^ 9 -^^^^ — ^^^ 



I ^\ \\ / ® \\ 



11 14 91 58 14 17 9 85 



1231 Males. Total 2141. 910 Females. 



Fig. 122. — Second census at Tierra Blanca in 1908, showing condition In the 

 population as a whole and the persistence of isolated groups in previous censuses. 



