"i8 93 .] THE BRITISH NATURALIST. 161 



phenomena than we possess at present. I think the close association 

 of melanism and manufacturing activity has been overstated. My 

 own slight experience would rather lead me to believe that where the 

 fumes and smoke of mines, or mills, or 1 works ' of any kind are strong 

 enough to have any influence at all, they exterminate rather than 

 ' melanize,' and I think that rather better evidence might be produced 

 for the association of these melanic forms with a peaty soil, with 

 heather, or with woodland darkened by pine or larch, than with the 

 perturbing effect of chemical fumes or coal smoke. Then again, I 

 think we require more exact and contemporaneous evidence as to the 

 change said to be so recent in many of the species under discussion, 

 we want testimony, going back say fifty years, from a score or so of 

 competent observers in as many districts in Great Britain as to the 

 change in such a species as Amphidasys betularia. In localities in- 

 fluenced by the products of manufacturers, for this it is probably vain 

 to hope, but there are many points which strike me as never having 

 been adequately discussed in this phenomena of recent melanism, as, 

 for instance, why do the Geometrae seem so especially subject 

 to it ? Noctuse, we know, are very susceptible to melanism of the 

 northern kind ; why, then, are not they equally affected by the 

 supposititious inflences of manufacturing agencies ? Again, is it 

 not a fact that species, whose habitat is sylvan, are the principal 

 sufferers ? What influence may the great increase in the planting of 

 pine, larch, and spruce, during the last century have had ? It has 

 certainly made our woodlands darker and denser than when they were 

 composed of the more properly indigenous oak, and birch, and beech. 

 Again, we have a mass of evidence of melanism rampant round large 

 towns in Lancashire and Yorkshire.* How far may not this be due to 

 the fact that most entomologists live in towns, and work within easy 

 distance of them, and that there are probably more observant 

 entomologists in the towns of Lancashire and Yorkshire than in any 

 other district (except London) in the Kingdom ? These are some of 

 the questions which occur to me, questions, perhaps, more easily 

 asked than answered. At any rate, I feel that the case is very far 

 from being ripe for dogmatic assertion about smoke, clouds, or any 

 other agencies. And again, I would ask why no practical and enter- 

 prising entomologist has not made some of these species the subject 

 of direct experiment. Take A. betularia, which seems to be one of the 

 clearest and best known cases. As to glacial epochs and post 

 Tertiary faunas we must fain theorize, but here where we have 

 phenomena proceeding under our very eyes, experiment is clearly 

 the road to truth, experiments conducted after the manner of Mr. 



* Melanism prevails around N ewcasile-on-Tyne where their are proportionately very few 



Entomologists. — Ed. 



