244 



The Mechanism of Evolution in Leptinotaesa 



Figure 37 shows in schematic form the results from the progeny of a single 

 pair, both of which were in aspect type 1 pronotum. A pair of wild beetles with 

 black pronota from Chapultepec ^ were bred in 1905-06, and gave in F^ the array 

 shown in the diagram, with some fluctuations of each of the five types which 

 are represented. Of the five types found, examples of each were mated with 

 likes. A pair of black type 1 was mated (A), and gave in F, equal numbers of 

 black A' and a type 2 form A". Each of these when inbred gave in F3 : from 

 the black of A' came 100 per cent black, and this continued to breed true, while 

 from the type 2 A" came black A" and type 2 again A" a, in about equal numbers. 

 The blacks in F3 A" bred true for three generations, while the type 2 A" a split 



F7. 



LA'I 



F6 



A'l 



4Plil 



mm 



n 



tv «^ « «l «l «l 



m 



I A' 



F4 



Fs 



Fz 



Fi 



m.mmmm 



A' 



/V" i I A"ab I A"ac 



I D"ca. i_JZr^ 1 . I 1 



I J r 



E"Q 



A' 



A'.'l — , I A"a 



m mmm 



A'l — , — I A" J 1 r 



m^ 



D"b D"a. D"c F'ca E'c E"cb 



\ J . .. 



^ ^ ^ E"c E"b E"a 



M>m, mmm-m 



XD. 



Fig. 37. — Schematic results showing complex nature of a pair of L. multitwniata, 

 having a pronotum of biotype 1 and heterozygous in nature. 



into blacks A"a and type 2 again, some of which A"ac continued to breed true, 

 and some A" ah split again. In Fj of type 2 two pairs were mated and only one 

 gave progeny, and in Fg two pairs were again mated and only one gave progeny, 

 but in F4 six pairs out of eight gave progeny from type 2 matings and two gave 

 the behavior shown in A"ac, and four that of A" ah. Two races, stable, without 

 selection were obtained from A. 



From B no pairs were mated, but from C in F^ out of three such matings one 

 bred true and gave a stable race. From D, of which I bred only one pair, two 

 types appeared in Fg, a low extreme of biotype 4 (D') and a biotype 3 (D"). 



^ In all tests of materials from nature the larvae were taken and reared, and the 

 sexes isolated at emergence, so that the females were in all cases certainly virgin. 



