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Show 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 tins genus is entirely confined to the Palse-arctic region, and in this respect it is peculiar, among large and important genera, with Melitcea and Erebia, which have an almost exactly similar distribution, though Erebia is more arctic than either of them. In the Nearctic region, which, as I have before mentioned, can hardly be separated from the Palsearctic region on the ground of any peculiarity among the Lepidoptera, it is confined, as is Erebia, and, with trifling exceptions, Melitcea, 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 within 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 can have any complete knowledge of the natural productions of these extremely distant, inhospitable, and elevated regions. Parnassius in one respect is unique among Rhopaloeera, 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. Eversmanni 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. |