298 The Inheritance of Wing -Colour in Lepidoptera 



Conclusions. 



1. The observations of Hamling and Harris seemed to show that 

 although the factor for melanism in Hemerophila abruptaria is dominant 

 to that for the type form, yet the ratio of type to melanic is not always 

 a simple Mendelian phenomenon. 



2. Nevertheless, a repetition of their work shows a ratio of type to 

 melanic in the first broods, very closely approaching the equality expected. 



3. In another set of matings, which produced the second broods, 

 the mortality for various reasons was over 75°/^. In this case, as in 

 the experiments of Hamling and Harris, the ratio was nearer 3 melanic 

 to 1 type than equality. This suggests that there may have been a 

 selective mortality in favour of the melanic insects, which disturbs the 

 normal ratio. 



4. That a certain constitutional strength seems to accompany many 

 melanic forms has been pointed out by other authors, and attention is 

 here drawn to the fact that this would account more easily than other 

 hypothesis for the rapid replacement of type by melanic varieties. 



In conclusion I have to thank the British Association for a grant of 

 £25 which helped to defray the expenses of 1920-1, and Miss Helen 

 Moodie for her help in the routine work. I am also indebted to Professor 

 Punnett for reading the MS. of the paper. 



DESCRIPTION OF PLATE XXVIII. 



Hemerophila abruptaria and ya,r. /uscata, Tutt. Natural size. 



1, 2. H, abruptaria. Typical $ $ . 



3, 4. H. abruptaria. Dark $ $, showing the same depth of colour as the typical ^. 



5, 6. H. abruptaria. Typical ^ ^. 



7, 8. Var. fuscata. Melanic $ $ , in which the ground colour and that of the band on 

 the fore wings are the same. 



9, 10. Y&r. fuscata, Melanic <J ^, the band in which is slightly lighter than the ground 



colour. 

 11, 12. Var. fuscata. Melanic ^^ from the second broods. These insects are smaller 

 than those of the earlier broods, and the central area of the fore wings is some- 

 what paler. 



