GENERAL ACCOUNT OF BUTTERFLIES 



coalescence, of adjacent veins. Thus in many but- 

 terflies radius of the fore wings instead of being 

 five-branched is only four-branched or even three- 

 branched (Fig. 7). In a case of this kind the 

 designation R 4+5 indicates that veins R 4 and R 5 

 have grown together to form 

 a single vein. 



In the hind wings of all 

 butterflies the radius differs 

 greatly from that of the fore 

 wings. By referring to the 

 venation of Sthenopis (Fig. 

 6) it can be seen that at the 

 first forking of radius the 

 vein is divided into two un- 

 equal parts ; one of these 

 is vein R„ the other gives 

 rise to the remaining four 

 branches of radius. This 

 second part is termed the radial sector, and is 

 labeled R s in the figures. In all butterflies the 

 branches of the radial sector of the hind wings all 

 coalesce so as to form a single vein, and vein R, 

 coalesces with the subcosta. This is well shown in 

 the hind wing of Papilio (Fig. 8). It will be ob- 

 served that in this wing vein R T soon after its 

 separation from vein R s joins vein Sc and the 



13 



Fig. 7. — Venation of the 

 wings of a metal-mark. 



