136 Inheritance of Wing Colour in Lepidoptera 



The melanic form of B. abietaria, though very dark, is not so sharply 

 differentiated from the type as is sometimes the case This is partly 

 because the shade of the type form varies considerably, but chiefly 

 because it is by nature a dark species, Plate VI, figs. 1 and 2, show the 

 darkest specimen of the type insect met with, which is almost certainly 

 identical with var. seHcearia Curt. This variety only occurred occa- 

 sionally, and was usually extracted from melanics. It is so dark that it 

 shows traces of black veining like the true melanic form, and the casual 

 observer might possibly mistake it for that variety. The difference is, 

 however, manifest, for the whole insect is browner than the black 

 form, and appears slightly mottled especially on the hind wings. The 

 three black spots on the costa can be always faintly discerned, and 

 the deep black lunules along the margin are also visible. These lunules 

 are especially conspicuous on the hind wing where they form the most 

 distinctive feature, by which the type insects can be characterised. In 

 the melanic form (figs. 9 and 10) the wings of the female are a uniform 

 velvety black, those of the male slightly browner, and except the discal 

 streak and the veins which are traced in deeper black there are no 

 lines or markings of any description. This black veining is especially 

 evident in insects which are freshly emerged, but it fades on drying. 

 The type strain with which the melanics were crossed, came from pupae 

 collected in two separate districts in the New Forest. They varied in 

 colour and markings, sometimes being as dark as insect No. 3, which 

 was extracted from melanics, but thS majority were like insects Nos. 5 

 and 6. In two cases wild insects emerged as pale as No. 8, and were 

 a lovely golden brown. The colours seem to get progressively less 

 golden and more grey, as the insect gets darker. No. 7 is one of a 

 long series of typical insects, bred by Mr Harwood from New Forest 

 pupae, the colour of which was almost uniformly like that of the specimen 

 illustrated. On the whole, the females as a rule appear slightly darker 

 than the males. 



The melanic strain came from two batches of larvae collected from 

 the yew trees at Dorking, one in 1915 and the other in 1916; in the 

 following year these produced families '17^, 17 B, etc. as is seen from 

 the accompanying table. Each family is labelled with a distinctive 

 letter and the year in which the ova were laid. 



The larvae proved very hardy, especially the melanic race. The ova 

 were hatched in metal boxes, and were transferred a fortnight later to 

 yew in the ordinary type of glass breeding cylinders, where they remained 

 until ready to hibernate. During the winter, they were sleeved on yew 



