INTRODUCTION. 



Whilst I was engaged in the preparation of this, the third volume of my 

 monograph of the Rhopalocera of Java, my collaborator P. C. T. Snellen 

 died. The systematic portion of this work, however, had already been completed 

 by him, so that its continuation need not, therefore, be interrupted on that 

 account. On the other hand I shall surely miss the aid of his extensive know- 

 ledge of the Malayan lepidoptera. 



Before proceeding to a general discussion of the Rhopalocera, now to be 



considered, in the manner followed in the two previous volumes I deem it 



necessary to point out that for comparison I have been able to avail myselt 



of the work of Prof. Dr. Seitz " Die Gross- Sckmetterlinge der Erde " in which 



the Malayo-Australian Danaidae and Satyridae have already been dealt with by 



my collaborator H. Fruhstorfer. For although this book, intended chiefly for 



identification, differs totally in character from mine, this does not prevent it from 



being very useful for my work. I do not, indeed, agree in every respect with its 



contents, especially as regards the practice of basing a subspecies on every 



slight difference in colour or form of wing in butterflies of the same species 



and to apply to such forms distinct names. This method of procedure is at 



present much in vogue in the domain of entomology and since I do not follow 



this fashion kind critics have pretty clearly expressed the opinion that as I pay 



so little attention to local forms I do not, evidently, keep in touch with the 



prevalent attitude in this science. The matter, however, is this that this attitude I 



conceive to be a fashion or an expression of exaggerated speculation rather than 



a serious contribution to science. Where real local forms occur these do not 



escape my attention, but a slight difference of colour, even when it occurs in 



different localities, does not, in a scientific sense, merit the name of local form. 



It is a case of an opinion based on f;Use premises which, in its practical 



I 



