62 
THE NATURALISTS’ JOURNAL. 
be so nearly allied to that of western Europe, might it not be as 
possible for the Diurnal Lepidoptera of North America to have 
been derived from the eastern portion of the pakearctic region, 
as from the western ? Personally I think this is much more 
probable, for then, instead of the insects having to traverse an 
“ Atlantis ” three thousand miles in length, they could much 
more easily have gained access to the new domain by means of 
Behring Straits. In support of this theory I may say that as 
many palaearctic butterflies occur in that portion of North 
America nearest Asia, as there are in that adjoining the 
Atlantic Ocean. 
The number of species of Diurnal Lepidoptera occurring in 
the nearctic region (which comprises the whole continent of 
North America, with the exception of Mexico), is, in round 
figures, isix hundred and fifty. It is thus a richer hunting 
ground for these grand insects than the palaearctic region, 
which is of much greater dimensions, but only counts about 
five hundred and fifty different kinds within its limits. 
The number of species found in Europe alone is just about 
three hundred, and of this figure nineteen also occur in North 
America ; while there are as many as twenty-six genera common 
to both continents, the total number of genera occurring in the 
nearctic region being seventy-six. 
The chief characteristics of the Diurnal Lepidoptera of the 
North American continent, consist in the following :—ist. there 
is a “ beautiful brigade” of large swallowtails, numbering in all 
twenty four species ; 2nd. the Pieridce present a fine array of 
forms ; 3rd. the LycoenidcB and Nymphalidce are about as 
numerous in proportion to their European relatives, but 4th. 
the Satyridce do not appear to be so well represented, while 5th, 
the tlesperidce form the most numerous family of North Amer¬ 
ican butterflies, the number of species belonging thereto con¬ 
stituting more than one fourth of the whole. 
I may here remark that the editor is quite correct in assum¬ 
ing that our common white butterfly {Pieris raped) owes its 
appearance in North America to the agency of man, it having 
been introduced into that continent in i860, since which date 
it has multiplied and extended its area of distribution to a 
wonderful degree.* It may interest readers to know that the 
following species of British butterflies also occur in North 
America, namely, Papilio machaon. Papilio sinon, (P. podalirius, 
now extinct in England), Pier is napi\ Vanessa antiopa , Pyrameis 
utlanta , ar d Pyrameis cardui. On the other hand, the following 
two species of North American Rhopalocera have occured as 
occasional visitors in the British Isles, namely, the great Danais 
* See S H. Scudder’s “Introduction and spread of Pier is rapx in North 
America, 1860-86/' with a large map, 4to., Boston, 1S87. 
