1899.] GROTE — SPECIALIZATIONS OF LEPIDOPTEROUS WIXG. 35 



thoas, SO that I cannot distinguish the two in any way, and I must 

 suppose this generic title to be invalid. 



In all these generic types of the Papilio group the third radial 

 branch arises just opposite the point of junction of the discal 

 cross-vein, with a tendency to remove beyond it. The progress of 

 this branch along the radius, outwardly, may be apparently taken 

 as an index of the specialization. In the Papilionides there is a 

 general correspondence between the movement of this vein and the 

 specializations of the abdominal field of the secondaries. The 

 bending of the internal vein of hind wings is secondary in its 

 nature, has been probably attained along divergent lines, and is a 

 separate and well-marked feature in the specializations of the wings 

 of the Papilionides. 



The question as to the value of generic characters becomes sim- 

 plified when we reflect that there is no criterion, save that of 

 quantity, by which we can divide them from specific characters^ 

 For practical purposes it is well to break up such extensive genera 

 as Papilio, and to do so we must take slighter variations as the 

 basis of the division. It may be remembered that none of our 

 categories could apparently exist except for "missing links," and 

 our species thus appear as the momentary results of an average of 

 arrested development, with wider or narrower breaks between 

 them. This is one of the irrelevant generalities which it is well to 

 bear in mind, in order to avoid insisting too categorically upon the 

 absolute value of our divisions and terms. 



The generic types above discussed appear to group as follows : 



Iphiclides. Papilio. L^ertias. Priamides. 



Jasoniades. Menalaides. Ithobalus. 



Euphoeades. Achillides. Parides. 



Calaides. Iliades. 



Heraclides. 

 =: Troilides. 

 Orpheides. 

 Nestorides. 



Systematic Position of the Papilionides. 



The argument as to the rank and position in the system of the 

 Papilionides may be recapitulated here : All the generic types in 

 the Parnassi-Papilionidae that I have been able to examine have 



