28o 



PRODUCTION OF RACES AND SrECIES IN LEPTINOTARSA. 



in the second or hibernating generation, and both died during hibernation, so 

 that I have had no opportunity to make cultures. 



One of the rarest of the extreme variations from decemlineata is the form 

 tortuosa, which, however, must not be confounded with some of the somatic 

 variations of decemlineata, that often exactly resemble it. It seems to be 

 confined to the south, and only once have I obtained it north of the Ohio 

 River. Two specimens, male and female, were found in a lot of decemlineata 

 from Georgia in 1902, and were reared, giving a pure tortuosa progeny of 18 

 males and 16 females, and from these I again reared a second generation of 

 24 males and 33 females, pure tortuosa. These hibernated, and there emerged 

 in May, 1903, 6 males and 7 females, which gave a brood consisting of 31 

 males and 30 females. This breeding was continued until August; 1904, 

 when they were all destroyed. Crosses were also made between tortuosa 

 and decemlineata, but not with ease, and such crosses gave a true Mendelian- 

 like splitting. The procedure and results of this experiment with tortuosa I 

 can best show in the form of the diagram given in text-figure 21. 



1 



11 



in 



IV 



V 



VI 



1 ,? , 6 $ TORTUOSA ae parents. 



J- 



TORTUOSA 



is,?,, 16? 



TORTUOSA 



24 J- , 339 (crossed with decemlineata) 



TORTUOSA 

 26,?,, 219 



TORTUOSA 

 34,?,, 42$, 



TORTUOSA 

 10<?,| 149 



HYBRIDS 

 22,?, 209 



TORTUOSA DECEMLINEATA 

 6 



TORTUOSA TORTUOSA DECEMLINEATA 



20c?, 199 10,?, M29 41,?, 409 



TORTUOSA Killed 



Text-figure 21. 



As far as discovered, tortuosa behaves like a species, handing on its charac- 

 ters unchanged to its progeny for six generations without selection other than 

 isolation from other species. In the culture full opportunity was given for 

 promiscuous crossing such as occurs in nature. 



A variation which arose from decemlineata obtained at McPherson, Kan- 

 sas, appeared in my culture in June, 1904. This was rubrivittata, of striking 

 form and coloration, of which there was a single male. The parents, which 

 were collected in July, 1903, near McPherson, Kansas, were sent to Chicago 

 and reared in a second generation which was normal ; they hibernated until 

 May, 1904, and then emerged, reproduced, and among the progeny was this 

 single male rubrivittata. This male was crossed with a female decemlineata 

 from Chicago, and gave a hybrid brood intermediate in character between the 

 parents. Three males and one female of this lot escaped the general exter- 



