THE DIUBNAL LEPIDOPTER A. 



433 



splendid tropical forma in size and brilliancy : but, on the other 

 band, the number of peculiar forms is considerable ; and the tro- 

 pical representatives of boreal genera by no means surpass those 

 of temperate regions ; and I have myself observed that on com- 

 paring Indian and European representatives of the same species 

 the Indian specimens are generally smaller, owing probably to the 

 more rapid development of the larva? in a warmer climate. 



With regard to the peculiarities of distribution within the 

 limits of the Palaearctic region, we have, first, the Arctic 

 fauna, which is practically circumpolar ; next the central fauna, 

 stretching through the vast plains of Central Asia-Europe, and 

 in which we may also include the Alpine fauna. The bulk of the 

 central species are bounded to the south by the Alps and Pyre- 

 nees ; and hence the fauna of Spain is much poorer than that of 

 France, and that of Italy than that of Austria. South of the 

 Alps, in Europe, we find the Mediterranean fauna, which has 

 several little groups peculiar to itself. There is probably a south- 

 central steppe fauna in Central Asia ; but too little is known of 

 that region to enable us to say more than that it produces several 

 peculiar forms of high interest, e. g. Hypermnestra. The south- 

 east of Europe is much richer in species than the south-west ; for 

 there are fewer obstacles to the southern spread of the central 

 fauna in that direction. 



Still it is difficult to account for the much greater number of 

 species in East-central than in "West-central Europe. 



The Alpine species are scarcely represented at all in the moun- 

 tains of the extreme south of Europe ; and not a single truly 

 Alpine species is yet known to occur in the mountains of North 

 Africa. The extrinsic elements of the Palaearctic fauna consist, 

 first, of isolated Nearctic and Indian forms in Japan and Mant- 

 churia (Midea, Fapilio, &c); second, of a few Indian forms in 

 Eastern Europe (Neptis, Danaus, &c); and, third, in a few African 

 forms in South Europe and North Africa (Gharaxes, Callosune). 



It is very difficult to estimate the real number of known species 

 occurring in the Pahearctic region, on account of the division be- 

 tween this and the Indian region intersecting China and the 

 Himalayas ; but they may be set down as about 630 * at a very 

 moderate computation. Dr. Sclater gives the area of the Palae- 

 arctic region as 14,000,000 square miles, and the number of spe- 



* Species ocourring in more than one region are enumerated under both in 

 this paper. 



