W. BOWATER 803 



Mr B. H. Crabtree is now conducting an experiment, commenced in 

 1912, which apparently makes this certain. 



10. Hemerophila abruptaria. Mr Harris^ and Mr T. H. Hamling^ 

 have shown that the dark form is a Mendelian dominant. 



11. I can discover only two records of experiments on Odontopera 

 bidentata which throw light on the heredity of its melanic form : — 



a. A paper by the late Mr T. H. Hamling^ in which it is recorded 

 that a black J taken at Methley deposited ova, which produced 

 70 black and 6Q type imagines. From this fomily inbred, 14 successful 

 pairings are reported : 



Parentage Imagines 



These results can be explained, but only in a way which would be un- 

 justifiable were it not that a much more extensive experiment has now 

 been made, which supports the following argument : 



The first family was mixed, therefore neither parent was dominant. 

 The original $ parent being black must therefore have been hetero- 

 zygous ; and the </ either similar ; or type (recessive). In the former 

 case, the offspring should be 75 per cent, melanic (heterozygous and 

 homozygous) and 25 per cent, type ; and in the latter, 50 per cent, 

 melanic (all heterozygous) and 50 per cent. type. 



The comparative frequency of occurrence of the two forms in nature 

 makes it more likely that the </ was type ; and the fact that 136 moths 

 were reared from the 146 ova deposited, makes this almost certain, 

 because the melanic form seems to be the more hardy, and of the 

 10 ova which failed to reach maturity, the majority would probably 

 be type, and even if all were black, the numbers would only be 80 : 66. 



Thus it seems that all the 70 blacks were heterozygous, so we should 

 expect if X if to give 75 per cent. M and 25 per cent. T, but the 

 mortality amongst the larvae was very high indeed, and would account 

 for the hardier melanic outnumbering their type brethren by more 

 than 8:1. 



^ Proc. Ent. Soc. Lond. 1904, p. Ixxii. 



2 Trans. City of Lond. Ent. Soc. 1905, p. 5. 



3 Trans. City of Lond. Ent. and Nat. Hi.-it. Soc. 1903, pp. 40—43. 



