1886.] MR. H.J. ELWES ON THE GENUS PARNASSIUS. 15 
interesting problem for the future to discover how the organs of 
such curious species as P. acco, P. charltonius, P. imperator, or 
P. tenedius are produced, and why insects so very similar in appearance 
as P. jacquemonti and actius, or P. charltonius and imperator, have 
such very differently shaped pouches. 
The distribution of this genus is entirely confined to the Pale- 
arctic region, and in this respect it is peculiar, among large and 
important genera, with Melitea and Eredia, which have an almost 
exactly similar distribution, though Hreéia is more arctic than either 
of them. Inthe Nearctic region, which, as I have before mentioned, 
can hardly be separated from the Palearctic region on the ground 
of any peculiarity among the Lepidoptera, it is confined, as is 
Erebia, and, with trifling exceptions, MJelitea, to the Rocky 
Mountains and country west of them. It is most numerously 
represented in the mountain-ranges of Turkestan, Southern Siberia, 
and the Himalaya, having only three species out of 23 in Europe ; 
none in North Africa; none witiin the Arctic Circle, though 
P. mnemosyne and P. eversmanni come within a few degrees of it. 
Of all the sections into which I have divided the genus, only two, 
namely the apollo and mnemosyne groups, have a wide range, and 
only these two have developed any marked specific differences ; all 
the rest of the groups, most of which are monotypic, being confined 
to limited areas in Central Asia. It is almost certain that several 
species remain to be discovered in the mountainous regions of 
Mongolia, Tibet, and North-western China; but many years must 
elapse before we cau have any complete knowledge of the natural 
productions of these extremely distant, inhospitable, and elevated 
regions. 
Parnassius in one respect is unique among Rhopalocera, namely, 
that though in a great part of its range a genus most characteristic 
of mountain-ranges, and most abundantly represented where, as in 
Ladak and the mountains of Khokand, the climate is of an almost 
Arctic character, yet it does not occur anywhere in the Arctic 
Regions. Colias, Argynnis, Erebia, and Chionobas, with which 
Parnassius is generally associated in Europe, Asia, and America, are 
all typically Arctic genera. Why, then, is Parnassius, which finds a 
home at as great an elevation as any other known butterfly, absent ? 
Though in Europe generally looked on as mountain butterflies, 
several of the species, as P. apollo, mnemosyne, bremeri, eversmanni, 
and nomion, are also found in low and wooded districts. Hversmanni is 
said to be an inhabitant of deep bogs. Mnemosyne, though ascending 
the Alps to 5000 feet ur more in Western Central Europe, in Eastern 
Europe is found commonly in the steppes. Apollonius also occurs 
both in saline steppes and high mountains. 
The following Table shows the general distribution of the species, 
but it must be understood that almost everywhere the species are 
found in somewhat restricted localities, and not generally through 
the country. 
