74 Inheritance of Melanism in Tephrosia (Ectropis) 



TABLE XII. 



Homozygcnjbs Type x Homozygous J^ype {mm x mm). 



Melanlcs Typea 



Family Parentage Males Females Totala Males Females Totals Melanic 



p a^xa^ — — — 14 12 26 — 



q 6$x6^ — — — 29 26 55 — 



r a?x6<J — — — 25 18 43 — 



Actually reared ... 124 



Theoretical result ... 124 



The result of mating homozygous melanic insects together may be 

 seen by referring to Table V above, where it will be perceived that as 

 the outcome of such pairings nothing save melanic insects appeared. 



Thus it seems that, no matter whether the type insects are obtained 

 from localities totally uncontaminated with melanism or from stations 

 where that is rampant, the result is the same; melanism in the species 

 Tephrosia crepuscularia is inherited strictly in accordance with Men- 

 delian expectation. From this we may draw the conclusion that, as 

 far as that character is concerned, typical insects from all sources are 

 genotypically the same. 



III. The Inheritance of Melanism introduced by Tephrosia cre- 

 puscularia VAR. DELAMERENSIS WHEN THAT SPECIES IS CROSSED 

 WITH T. BISTORT ATA. 



As the source of the Tephrosia histortata utilised in the experiments 

 I selected a Wateringbury brood (designated hereafter as Family I) 

 reared from a wild female. Needless to say this brood ^ was, as far as 

 melanism was concerned, composed of homozygous recessives. Reci- 

 procal crosses were made between insects of this origin and T. crepus- 

 cularia of the delamerensis form chosen from the two broods labelled 

 B' and a above. As will be remembered, B' included only homozygous 

 melanics whereas "a" provided homozygous types as well as hetero- 

 zygous melanics. 



The following tables give concisely, as far as colour and sex are con- 

 cerned, the indications of the original hybridisation experiments. Except 

 for the abnormal sex results set out in Table XIV A, which form the subject 

 of a subsequent paper, they call for little comment. They are in practical 

 agreement with Mendelian requirement although perhaps the proportion 



1 Experimental evidence exists to the effect that in T. histortata as in T. crepus- 

 cularia melanism is dominant. 



