2 Messrs. H. J. Elwes and J. Edwards on 
visional, yet we hope that this paper will be of some 
assistance to others in determining the species of this 
difficult genus. 
It should be stated that Elwes is solely responsible for 
the remarks on geographical distribution and habitat, as 
well as all statements appearing in the first person 
singular; whilst Edwards is responsible for the grouping, 
tabulation, and description of the species, and the whole 
of the dissections and drawings. 
In preparing this paper we have carefully studied the 
rich collections of Messrs. Godman and Salvin, Mr. J. 
H. Leech, and the British Museum, as well as Elwes’ 
collection, which contains a good series of almost all the 
Kastern species. We have to thank these gentlemen, 
as well as Herr P. C. T. Snellen, of Rotterdam, and 
Mr. de Nicéville, of Caleutta, for the loan of many 
doubtful specimens for examination. Mr. Moore has 
kindly furnished the names of some species which were 
in course of description in his work, and we are thus 
enabled to avoid the creation of synonyms. 
The main feature of this attempt to deal with these 
insects is the employment of the structural characters 
afforded by the male genitalia. If we except the work of 
Messrs. Godman and Salvin, no large amount of prac- 
tical use has hitherto been made of these characters in 
this country, and therefore a few remarks on the general 
subject may not be out of place. Connected as these 
accessory organs of generation are with the function of 
reproduction, their importance in the economy of the 
organism will be readily conceded, and experience proves 
that they present great stability of form in the different 
groups which we are accustomed to regard as species ; 
whilst it is an open question whether they are not of more 
importance as indications of natural affinity than cha- 
racters derived from colour or markings, even when the 
latter are very decided. At the same time, the use made 
of these characters must be rational, mere differences of 
degree are of no more account here than elsewhere, and 
if trivial individual differences are taken as conferring 
specific rank, such a course can lead to nothing but dis- 
appointment and disgust on the part of those who have 
to work from our descriptions. Taxonomically con- 
sidered, the real value of the study of the primary 
sexual characters consists in the removal of individual 
