XXXVIII 



amount of heat than the wet peaty soils of the north, and to that, in 

 in conjunction with the fact that there is more rain, and consequently 

 less sunshine in the north, is melanism entirely due. Why even in the 

 South of England darker varieties occur on cold wet lands than on 

 light dry soils, which absorb a greater amount of heat from the rays of 

 the sun. Extreme heat has also a tendency to produce white varieties 

 of the Blues, thus we find a white variety of Cory don in Andalusia 

 named Albicans. But it may well be asked what effect has heat on the 

 Whites ? The tendency is to produce yellow varieties, such as the 

 variety Nov-anglice of Pieris rapce. 



Pieris napi affords another instance of the effect of strong sun- 

 light. The spring brood which occurs in May is much darker and 

 more strongly marked than the summer brood which occurs in the 

 month of July, when the days are longer and the sun more powerful. 

 On the Alps a very dark variety of the female named Bryonia occurs. 

 Besides the fact that the brightest colours which exist in nature are 

 those which we see in insects and birds that are most exposed to the 

 direct rays of the sun ; the brightest parts of these birds and insects 

 are those which catch these rays in a greater degree than others . 

 hence the upper sides of butterflies are more highly coloured than the 

 under, a notable instance is found in Vanessa io. 



The question of nomenclature is a very difficult one to decide. 

 The British Association adopted certain rules for Zoological nomencla- 

 ture. The most important of these rules was that the 12th Edition of 

 the Sy sterna Natura of Linnaeus should be taken as the starting point. 

 Surely the last and carefully revised edition of so great a work is a 

 safer starting point than an earlier, and admittedly imperfect edition. 

 Mr. Kirby in the supplement to his great Catalogue of Butterflies 

 goes back to the 10th Edition. But if we go back at all, why not 

 go still further ? Why not go back to the Fauna Suevica published in 

 1746. Surely if he goes back from 1767 to 1758, he may as well go to 

 1746. Then we shall have to adopt Ammiralis for Atalanta, and 

 Principissa for Lathonia, except indeed we go still further back to 171 7 

 and call the latter Cantabridgensi, Petiver. And surely the descriptions 

 given by Petiver and by Linnaeus in his Fauna Suevica, are equal in 

 point of merit, if not superior to those of Huffnagle. When Guenee 

 and Doubleday prepared their lists they examined all the authorities 

 for themselves, and rejected for various reasons the works of authors 

 whose figures or descriptions were unsatisfactory. Now-a-days an 



