NOTES OX THE MELANISM OF LAKENTIA MULTISTRiaARIA. 171 



sloping from an altitude of 1200ft. to 600ft. on the hill-top. Where the 

 food-plant, Galunn m.catile, grows more or less abundantly by the 

 stone walls, the species appears accordmgly. (2) In Defter wood 

 (700ft.), four miles east of the melanic region. The species is com- 

 mon, and (8) Two miles further east, on High Hoyland bank (600ft.) 

 it is also common. All the specimens that I have seen in these lower 

 localities are of a light form. Here, the vegetation is altogether more 

 luxuriant, the district very well wooded and well inside the wheat- 

 growing area. It follows that the lowland light form is not nearly so 

 exposed as the dark form on the hill-top. It is generally slightly 

 larger also. The upland race, however, must have endured exposure 

 for ages, and it is by some considered that melanism has only very 

 recently been developed." What then can be the cause of this develop- 

 ment ? If smoke be the agent it seems to act in the wrong direction, 

 for, on the hills where the dark race is found neither chimney-stacks 

 nor houses exist (except a few small scattered farms, the smoke from 

 which can have little or no effect), while down the Dearne valley many 

 mill chimneys are pouring forth daily black volumes of smoke upon 

 the surrounding hillsides, assisted by the grey clouds from the chim- 

 neys of houses in many villages, and yet, on these hillsides, where the 

 western winds carry most of this impurity, the light race only occurs. 

 I confess that I fail to see how smoke can be the agent, for, even if it 

 be allowed that the east winds carry as much smoke on to the western 

 slopes as the west winds do in the other direction, allowing smoke to 

 be the cause, we should expect to find melanism general ; bat one has 

 only to look at trees growing on the south Yorkshire uplands to be 

 very soon convinced as to the direction of the prevalent winds, for 

 invariably, in exposed places, they have practically a naked side to the 

 west, the branches hanging out towards the east. Geologically, how- 

 ever, the conditions are very difierent. The light race occurs on the 

 borders of the upper and lower coal measures, but directly the narrow 

 belt of the lower coal measure is passed, and the millstone grit is 

 approached, the species gives way to melanism. How the geology of 

 the district does influence the species may be hard to say, but all the 

 conditions must be considered when trying to solve knotty problems of 

 this kind. When melanism first appeared in the species I am unable 

 to say, but when I first noticed it, seven or eight years ago, while 

 walking upon the commons after a very heavy rain storm, I found 

 hundreds of the species drowned in the ditches, with many black 

 forms amongst them, and, since then, have obtained it every year, with 

 more or less success. From the above facts it is very evident that 

 melanism is well established on the Dearne watershed, also, I belie\e, 

 in the Meltham valley, and probably also in many other districts in 

 southwest Yorkshire, but it would be interesting to know how far this 

 tendency at present extends, and then watch its development in 

 districts where at present it is not in evidence. 



* Surely not in all cases. It is possible that in cases such as that mentioned 

 the melanism is as old as the hills and their present meteorological conditions. See 

 Melanism and Melanochroiwi in Britisli Lepidoptera, pp. 19-'il ; '23-24, etc. — Ej). 



