54 Melanism in Tephrosia consonaria 



which melanism was dominant, and in the other recessive to the type 

 form. It was then proposed to carry , out a chemical study of the 

 metabolism of the adult larvae and the pupae of these two species, in 

 the hope that some light might be thrown on the mechanism responsible 

 for such dissimilar phenomena, and possibly on the wider problem of the 

 chemical aspect of the laws of heredity. 



The history of the melanic form of T. consonaria (the Square Spot)' 

 is not without interest, the most important point being, that it has, as 

 far as I can ascertain, only been found in a single locality, and one 

 moreover which is very far removed from the traditional home of 

 melanic varieties, the Black Country. 



In 1892, E. Goodwin first found this form, subsequently described as 

 var. nigra^, in an oak wood at Wateringbury near Maidstone, and it is 

 said to have occurred there every year up to the present. The locality 

 is referred to by various authors as North Kent and West Kent, but 

 I understand the same oak wood is intended. The following interesting 

 details are given-. 



Ova obtained from normal females in the affected district yielded 

 about 10 °/q melanic; ova from black females yielded from S0°/^ to 75 "/^ 

 melanic, averaging about 50 %• Black $ x black </ gave 38 melanic 

 and 4 typical. 



Since it is clear from the experiments hereafter recorded that var. 

 nigra is a simple Mendelian dominant, these figures require some ex- 

 planation, because at first sight it might be thought that since normal 

 females give 10°/^ melanic, the black form is recessive. If var. nigra 

 is dominant, the least number of melanics that could be produced from 

 a type % mated to a melanic </ is 50 °/^ , supposing the male to be 

 heterozygous. The only explanation, therefore, is that the females were 

 fertilized by type as well as by melanic males. It is to be expected 

 that black females should give 75°/^ melanic, if both parents were hetero- 

 zygous. Black females giving 30 °/„ melanic might possibly be hetero- 

 zygotes paired to a normal male, in which case the expectation would 

 be 50°/^, bu,t it seems more probable that here again the females have 

 paired at least twice, that is to say, to a melanic and to a normal male, 

 and that the ova have been fertilized by the spermatozoa of both, which 

 have become mixed in the spermatheca. That males will pair several 

 times is well known. In 1918, for instance, I had two Abraxas gros- 

 sulariata males, var. varleyata. One of them paired no less than 9 times, 



1 Bankes, E. R., Ent. Mag., London, Vol. xli. p. 89, 1905. 



2 Doncaster, L., Ent. Record, Vol. xviii. p. 223, 1906. 



