1887.1 245 



variations presented by this species in England, it is primarily necessary 

 to have a numerous series, the authenticity of which is past question. 



And who can say how far the British specimens of several formerly 

 rare species of Lepidoptera latterly offered in considerable numbers for 

 exchange or sale, are the descendants of an ancient British stock, or 

 merely the great grandchildren of a modern experiment at acclima- 

 tization ? Unless a resolute and combined effort is made to check 

 these and other modes of tampering with our indigenous fauna, it 

 is possible that in a short time, lessons which ages of isolation have 

 accumulated for our instruction, will be obliterated for ever. 



But there are other natural causes which bring about modifications 

 in pattern and size besides the isolation which the ancient geological 

 disruption of Great Britain from the rest of Europe has effected. Of 

 these w'e may instance the effect of climate as one of the most im- 

 portant, and since ours is confessedly peculiar, we have a second test 

 to apply when instigating a comparison between our own and Conti- 

 nental examples. One form of climatal influence also is that which 

 depends on altitude. And this has been found to affect both botanical 

 and zoological organisms in a similar manner as latitude. Higher 

 latitude in fact corresponds to increased altitude. I will not, however, 

 pursue the subject further in its general bearings, but will take up a 

 few points worth noting in a cursory survey of our Diurni. 



The first butterfly in tlie British list is Papilio MacJiaon. This, though said 

 formerly to have existed in many places in England, is now closely restricted to one 

 or two localities, and, therefore, if it suryives, is tlie more likely to vary from the 

 Continental type. The genus to which it belongs presents aberrant tendencies in 

 the proportionate breadth of the black bands, in the length of the "tail" on the 

 hind-wings, and in the warmth or pallor of the yellow ground-colour. The size of 

 the eye spots at the anal angle of the hind-wing also varies. I do not know whether 

 British specimens exist illustrative of similar tendencies. The Corsican species, 

 P. Sospiton, appears to have become specialized through isolation, and to be a result 

 of the first two tendencies in Machaon. In the PieridcB, P. napi, deserves careful 

 and systematic attention at the hands of British entomologists. Not only does it 

 display a dimorphic form, differing in the two seasons of emergence, but occasionally 

 in Ireland, and doubtless elsewhere the $ presents a dingy appearance, with strongly 

 shaded ray-markings on the under-side, that reminds one much of the Alpine and 

 Scandinavian variety bryonice. This form, and the pale spring form of Vanessa 

 levana are considered by some to be surviving witnesses of the effects of the Glacial 

 Epoch. As the Scotch and Irish faunae seem to be strongly Scandinavian in their 

 features, it is probable that in these countries interesting varieties of the above Pieris 

 may turn up. 



Of the genus Euchloe, cardamines is our only representative. Among other 

 species the white of the under-side of the hind-wings turns silvery in hot southern 



