332 



THE WINGS OF LEPIDOPTERA 



who make this objection ignore the following taxonomic principle set forth 

 by the writer at the time the establishment of the suborders Jugatse and 

 Frenatae was proposed, viz. : 



"There will arise, I believe, in a work of this kind a necessity for distinguishing 

 between the essential characters of a group and those characters which are used by 

 the systematist merely to enable students to recognize members of the group. For 

 it seems to me that the essential characters of a group of organisms do not lie necessarily 



in the presence or absence of any 

 structure or structures, or in the 

 form of any part or parts of the 

 body of the living members of 

 the group ; but rather in the char- 

 acteristic structure of the progeni- 

 tor of the group, and in the 

 direction of specialization of the 

 descendants of this progenitor. 



"Thus, to use again the illus- 

 tration given above, the Jugatae 

 are essentially characterized as the 

 descendants of those ancient 

 Lepidoptera in which the wings of 

 each side were united by a jugum; 

 and they are also characterized 

 by a tendency towards an equal 

 reduction of the veins of the two 

 pairs of wings. While the Frenatae 

 are essentially characterized as the 

 descendants of those ancient Lepi- 

 doptera in which the wings of 

 each side were united by a frenu- 

 lum; and they are also character- 

 ized by a tendency towards a 

 greater reduction of the veins of 

 the hind wings than of the fore 

 wings, or, in other words, by a 

 tendency towards a cephalization 

 of the powers of flight. The fact 

 that in many of the Frenatas 

 the frenulum has been lost, does 

 not invalidate in the least the 

 truth of this characterization. The loss of the frenulum, however, in certain Frenatas 

 renders necessary the use of some other character or characters by the systematist as 

 recognition characters." 



The reduction of the radius of the hind wings. — Throughout the sub- 

 order Frenataj the radius of the hind wings is so greatly reduced that it 

 appears to be unbranched. This reduction of the radius is due to two facts ; 

 first, vein Ri coalesces with the subcosta; and second, all of the branches of 

 the radial sector coalesce so as to form a single vein. 



Fig. 340. — Wings of Bomhyx mori. 



