244 THE ENTOMOLOGIST. 



have only a small bit of a place, and the way we are hemmed 

 in here we can hardly prevent it, but I am getting some fresh 

 stock down from the hills, and we will soon get rid of the black 

 lot." 



Here, to me, was a new theory for melanism — may it not 

 apply to insects as well as to the larger animals ? At least it 

 is worth a little investigation and reflection. 



As for example, take the case of the environs of Paisley. To 

 the north of the town there were at one time — within the memory 

 of those still living — large tracts of virgin woodland interspersed 

 with pine and birch woods. Gradually the woods were cut 

 down, the heather burned, the land drained, and now all, or 

 nearly all, this extensive area ia under crops. But, as remarked, 

 not all — a very few small woods and moorland patches still 

 remain. And here the insect and bird fauna peculiar to pine, 

 heather and birch finds its last stronghold, huddled together no 

 doubt they are — to the extinction of many species once recorded 

 as frequent or common in the district. Small wonder, then, if 

 inbreeding is rampant ! In a small wood of scarcely ten acres, 

 with two acres of heather attached — virtually a fox cover — sur- 

 rounded by smiling cornfields, the heather and pine insects are 

 veritably on an island. 



And we do get quite a number of dark and black forms of a 

 variety of species — Thera variata : eighty per cent, are dark, twenty 

 per cent, are black, the type we rarely see. Eupithecia castigata, 

 we get a perfectly black form ; it was known at one time as the 

 " Paisley pug." Cidaria suffamata var. piceata is very frequent, 

 and the same may be said of one or two others confined in these 

 restricted areas. 



Take another illustration of the point. The August of 1909 I 

 spent my holiday collecting in the north-east end of the Island 

 of Arran. Now, there is no smoke or dirt there to support the 

 theory of their influence, yet I found melanic forms of various 

 species were common. In a long narrow rocky glen I came twice 

 upon small patches of billberry, only a few clumps to each 

 colony, and from each clump were disturbed several specimens of 

 C. popidata ; they were all much darker than the typical form, 

 and some of a unicolorous dark coffee colour. They never 

 settled on the rocks. The formation here is a dark slate-coloured 

 schist, with grey granite boulders in the burn, some of immense 

 size, but popidata always sought refuge by diving into the 

 heather or bracken thirty or forty yards up or down stream. I 

 did not meet with the species again until I struck the second 

 patch of food-plant, and then the same performance was repeated. 

 Inbreeding under these conditions was not only probable but 

 hardly avoidable, when we remember that the females of popu- 

 lata scarcely fly at all, so badly are they equipped in the matter 

 of wings. 



