1886.] MR. H. J. ELWES ON THE GENUS PARNASSIUS. 7 



the exception of two or three species, so slight that it would be 

 quite premature to write a monograph of the genus. But, partly 

 through the numerous scientific explorations whicli have been carried 

 on in Russian Asia of late years, and partly owing to the high value 

 placed on these Butterflies having encouraged the efforts of profes- 

 sional collectors in remote parts of Turkestan, so large a number of 

 specimens have reached Europe during the last five or six years that 

 a review of the genus is both possible and useful. The principal 

 object, however, in my work has been to investigate the functions 

 and structure of the horny pouch-like appendage which is found in 

 the female sex of the genus, and which seems to have been almost 

 entirely overlooked by most of those who have classified and described 

 the species. 



I had not appreciated the immense importance of this structure, 

 as a specific and generic character, until I received two years ago, 

 through the kindness of my friend M. Charles Oberthiir, of Rennes, 

 a specimen of the magnificent Parnassiiis imperator from East Tibet ; 

 but when I saw how strongly it resembled P. charltonius of West 

 Tibet in everything but the form of the pouch, whilst this organ 

 was remarkably different, I saw what appeared to me a structural 

 character of the highest value, and was led to an examination of the 

 whole genus, which, on account of the extreme tendency to variation 

 in size, and in the number and colour of the ocelli and markings — 

 which had previously been considered as the principal characters by 

 which to distinguish the species — was in a most unsatisfactory state 

 of confusion. 



The result of my examination is here given ; and I may say that, 

 however faulty and incomplete it may be, I have taken every pains 

 to bring it up to date, and have {)ersonally examined the principal 

 collections, both public and private, in Germany, France, Russia, and 

 England. I have thus been able to see, and to a certain extent 

 compare, large numbers of almost all the known s|)ecies, and though 

 my conclusions may not be accepted by those whose interest and 

 pleasure it is to multiply synonyms, and thus to increase the diflfi- 

 culty of the study of Lepidoptera, yet 1 believe that as far as it goes 

 it is based upon facts alone. 



My own collection, a part of which is now shown, contains about 

 400 specimens of the 23 species which I recognize in the genus, 

 and includes both sexes of every described species except two. 

 Though this number may seem large, yet I believe that it is not 

 more than half of what would be required to illustrate perfectly such 

 variable species as are most of the Parnassii, and though 1 have 

 a long series of many, I have kept no specimens which are not 

 necessary to illustrate some fact either of geographical distribution, 

 of variation, or of range of altitude and season. And such I imagine 

 should be the object of every scientific collector in any branch of 

 natural history. We too often see, in British collections at least, a 

 fixed number" of specimens exhibited in order to complete a row ; 

 but it is evident that whereas in some species of restricted habitat 

 and little or no tendency to variation, two or three pairs may be 



