ON MELANISM. 27 



identical, but where the melanism which occurs with us is quite 

 unknown. 



It cannot fail to be observed that these illustrations are all 

 taken from the Noctuidae. This great division has always 

 interested me most owing to the great variation in the species, 

 but in a superficial examination of the other divisions I have seen 

 the same rule hold good.] 



This at once fixes the fact that melanism is of purely British 

 occurrence, thereby upsetting the assumption of our theorists — 

 who indeed do not say so in as many words, but evidently desire 

 it to be inferred — that darker colouring and reduced size is a 

 feature of high northern latitudes. Notably it destroys Lord 

 Walsingliam's latest and ingenious theory that a large expanse 

 of white snow tends to produce it, for if it were true in Great 

 Britain it must of necessity be much more pronounced within 

 the Arctic Circle ; this, however, is not supported by actual 

 observation. 



Another feature in the examination of a large continental 

 collection, which still has to be explained, is tliat if we once 

 more return to our starting-point in Central and Southern 

 Germany, and turn our eyes southwards, it will be found that 

 the prominent features of lighter colour and fainter markings of 

 high northern latitudes again become apparent. Thus, inter alia, 

 in Sicily and Spain, Acronycta megacephala, Leucania lithargyria, 

 Apo7'ophyla australis, Agrotis triix, Noctua xanthographa, Hecatera 

 chrysozona (dysodea), Hadena peregrina, Anchocelis litura, A. 

 lunosa, Luperina dumerili, are all more or less lighter, with 

 glaucous shade of colour. In Asia Minor, Tripli(Bna ianthina 

 and Amphipyra t7'agopogonis are distinctly larger and more grey. 

 In Russian Turkestan, Asteroscopus nubecidosus and Calocampa 

 exoleta are quite ashy grey ; and Caradrina cubicularis, Charceas 

 graminis, Noctua flammatra, paler and lighter, with the same 

 tendency to glaucous. In fact nearly all tlie Noctuidse which I 

 have seen from the borders of the Mediterranean have this 

 glaucous tendency. 



The absence of melanism in continental Europe is not, 

 however, without its exceptions, for in the high alps of Switzer- 

 land, Styria, and Carniola it occasionally appears. Agrotis trux 

 there becomes identical with our A. limigera, Hadena dentina is 

 as dark as specimens from Shetland, Acronycta euphorbice becomes 



