482 Mr. W. F. Kirby on the 



so that the variety occurs in company with the type. A sexual 

 VARIETY only differs from a permanent variety in occurring only 

 in one sex. A sub-species is a permanent variety linked to its 

 nearest ally by intermediate forms, but which entirely replaces 

 the type in the localities in which it occurs. A sub-species is not 

 a true species, but under favourable circumstances it will become 

 so in time, as the varieties intermediate between itself and the 

 parent or cognate species die out. Finally, a species is a form 

 varying comparatively little in most cases, and generally distin- 

 guished from its nearest allies by constant differences in the 

 larva as well as the imago. 



In my recently published " Manual of European Butterflies" now 

 on the table, I divided Europe into thirteen arbitrary divisions, 

 for the purpose of better illustrating the geographical distribution 

 of the. species ; and before entering into their universal range, I 

 wish to generalise a little on the results I arrived at. My informa- 

 tion respecting Scandinavia, South Russia, Spain, France, Britain, 

 Austria and Switzerland is very complete ; with respect to the 

 other seven divisions I must generalise with caution. 



I. Iceland. — No more than six species of diurnal Lepidoptera 

 are known to me to occur in this country, viz., the polar sub-species* 

 of Culias Palceno and Phwomone, Colias Heckff, Argynnis Freyja, 

 and Chionohas Jutla and CEno, These are all northern species, and 

 are confined in Europe to Iceland and Lapland, with the excep- 

 tion of Colias Palceno and fhicomone, which are mountain insects 

 further to the south. 



II. Scandinavia, comprising Norway, Sweden, Lapland and 

 Finland. — One hundred and twelve species out of the 321 

 European species occur in this province ; nine of these appear to 

 be peculiar in Europe to this district ; thus leaving 1 03 occurring in 

 other countries. All our British species occur in this district ex- 

 cept C. Edusa, C. Hyale, L. Sibylla, A. Iris, M. Galalhea, H. 

 Tilhonius, E. Epiphron, E. Medea, P. Corydon, P. yEgon, P. 

 Actoeon, and C. Paniscus. The three latter species are represented 

 in Scandinavia by their nearest allies, which do not appear to 

 occur with us, though two have been reputed British. Thus, P. 

 yEgon is replaced by P. Argus, P. Actceon by P. Lineola, and 

 C. Paniscus by C. Sylvius. 



* I refer to Colias Pelidne and C. Nastes, which however may very possibly 

 be good species. 



t Having recently had an opportunity of examining some specimens in the 

 possession of Mr. Doubleday, which are undoubtedly the true C. Hecla of Le- 

 tebvre, I am now satisfied that the insect I described in my " Manual"' with some 

 hesitation as that species is certainly distinct, and probably new. 



