304 Heredity of Melanism in Lepidoptera 



In the results of the type x melanic crosses the same explanation is 

 probable. 



With regard to the melanic specimens recorded from parents both 

 type, it seems that one of the 4 $ 's had really paired with a black ^ . 

 Pairing occasionally occurs immediately the wings have dried, and all 

 breeders of Lepidoptera know how difficult it is to exclude all possi- 

 bilities of error when dealing with large numbers of pupae. On the 

 much less probable of the two original hypotheses, viz., that the 

 original ^ parent was melanic (heterozygous), some of the 70 would be 

 homozygous, and this would the more easily explain the preponderance 

 of melanics in their offspring. 



h. A paper entitled " Melanism in Yorkshire Lepidoptera," by 

 Mr G. T. Porritt^ 



A melanic female captured in 1904 deposited ova, which developed 

 into 6 melanic and 3 type specimens. From the black moths a large 

 brood was reared, which included 75 per cent, black specimens, and from 

 these again a considerable number were reared in which the percentage 

 of black was even greater. 



Mr Porritt has also repeatedly crossed type and melanic and found 

 the produce is about half and half of the two forms. These results are 

 easily reconcilable with the following experiment and the conclusions 

 drawn therefrom : 



In the autumn of 1909, on the advice of Mr Leonard Doncaster, 

 I commenced an experiment on Odontopera hidentata in the hope of 

 discovering whether the heredity of the melanic form of this species 

 followed any rule or law\ 



I commenced with a perfectly open mind on the subject, and in fact 

 had only a slight acquaintance with the various facts and theories of 

 heredity and variation. 



In November, 1909, 1 obtained 12 pupae, from which in April, 1911, 

 6 type and 6 melanic moths emerged. (Family 09.1). 



Two pupae were also obtained from a different source and produced 

 one type and one melanic specimen — 09.2 (see 1909 table). 



Six pairings were made, but in only two cases were the offspring 

 successfully carried to maturity: — 10.2 and 10.3. 



In June, 1910, I obtained 24 larvae bred from two melanic parents, 

 probably both of 09.1 family. The resultant moths are 10.4. 



1 Tram. Brit. Ass. 1906. 



