BEUTENMULLER, MONOGRAPH OF THE SESIIDvE. 



221 





Fig. 2. Part of a Hind Wii 

 course of Tracheae R,. 



of Sanninoidea exitiosa^ showing the 



fore wings ; the lack of reduction of the anal area of the hind wings ; and the unusual development 

 of the frenulum and of the frenulum hook in the female as well as in the male. 



" Although the members of this family in the course of their evolution have progressed far from 

 the primitive type of the order, they have kept closely together ; there is much less variation in the 

 structure of the wings than one would ex- 

 pect to find in a group so highly special- ^j^gpiirnriM 1 

 ized. 



" In the fore wings, veins R 4 and R 5 

 coalesce to a greater or less extent ; in some 

 genera, as Calasesia (Fig. 20) and Zenodoxus 

 (Fig. 21), the coalescence is complete, and 

 thus the number of veins is one less than 

 usual. 



" The anal area of the fore wings is so 

 reduced that in all the forms examined by 

 the writer only a single short vein remains 

 in the adult ; this is the second anal vein, a fact determined by a study of the wings of pupse (Fig. 1). 

 "A study of the development of the wings shows also that there is a striking difference in the 

 behavior of media in the two pairs of wings. This difference is the most remarkable feature 

 observed in the wings of this family. 



" In the fore wings, the stem of media is lost in the adult, as it is in other specialized Lepidop- 

 tera. In the pupa, the medial trachea is very distinct ; but in the adult there is no trace of the main 

 stem, and the branches are connected with the radial and the cubital tracheae. From this it follows 

 that the so-called discal cell of the fore wings is cell R + M. 



" In the hind wings, however, the stem of media persists in the adult ; but it has moved towards 

 the costal margin of the wing so that the so-called discal cell is cell M. The moving forward of the 

 main stem of media has been attained in the pupa stage (Fig. 1). 



" In the most generalized condition shown by the hind wings, there are three closely parallel 

 veins near the costal margin. As just pointed out, the third of these is the main stem of media and 

 its continuation M 1 . The other two veins are vein S c + R 4 and vein R s , as in other Frenatse. 

 This region of the wing is so narrowed that I have been unable to find any indication of the fork- 

 ing of the radius in the adult, but it is clearly indicated in the pupa (Fig. 2). 



" In some forms there are four 

 mmmgm anal veins in the hind wings. In 

 these cases it is probably the third 

 anal vein that is forked. I have not 

 had material to demonstrate this for 

 the Sesiidae ; but I have done so for 

 other families of the Frenatae. In 

 Pieris, although there is only one anal 

 v v vein in the fore wing of the adult, in 

 the pupa there are four anal trachese, 

 the third being forked (Fig. 3). 

 the fork J g When, therefore, there are four anal 

 veins, they maybe designated as 1st A, 

 2d A, 3d A u and 3d A 2 respectively. 

 A striking characteristic of this family is that in the female the bristles composing the frenu- 

 lum are consolidated as in the male. The females also possess a frenulum hook, but this is not so 

 highly specialized as that of the male." 



Fig. 3. Part of the Anal Area of the Fore \\ 

 of the 3d Anal Vein. 



