THE INHERITANCE OF WING COLOUR IN 

 LEPIDOPTERA. 



HI. MELANISM IN BOARMIA CONSORTARIA 

 (VAR. CONSOBRINARIA, BKH.). 



By H. ONSLOW. 



(With Plate XIII.) 



The inheritance of melanism in Tephrosia consonaria^ was described 

 in a recent communication, and further experiments with a similar form 

 of Boarmia abietaria will appear shortly. The work here detailed was 

 carried out with the melanic form o{B. consortaria (the Pale Oak Beauty). 

 The three melanic varieties just mentioned are peculiar, because their 

 origin is confined to the South of England. Black specimens of T. con- 

 sonaria, as well as those of B. consortaria first appeared in the same oak- 

 wood in Kent, and were not found far from that neighbourhood until 

 recently. Also the melanic form of B. abietaria occurs only in Surrey, 

 and occasionally in the New Forest. In none of these three species 

 did the melanism originate in the industrial districts of the North. 

 Lately, a melanic form of T. extersaria has arisen in Kent. 



In all accounts of the progressive spread of melanism, great stress is 

 laid on the fact that the melanic varieties have been found chiefly in the 

 " Black Country " of England, and in a similar district round Crefeld in 

 Germany. The deposit of soot and chemicals on the trees etc. in these 

 districts is supposed to give to the melanic varieties a survival value, on 

 account of their colouring, which there becomes protective. There seem 

 to be grave objections to this theory. In the first place some typically 

 melanic varieties have arisen in the rural districts of the South (as is 

 the case with the three species just mentioned), and other varieties are 

 found in equally rural parts of the North and West. Secondly, most melanic 

 moths are night flying, only occasionally being seen sitting on trees, 



* Onslow, H., Journal of Genetics, Vol. ix. No. 1, p. 53, Dec. 1919. 



