EXTERNAL ANATOMY. 



59 



the veins, of which there are five on each wing, diverging 

 from the proximal end of the wing, and giving rise to 

 smaller veins. These in ttirn divide into much smaller vein- 

 lets, which inosculate with each other and divide the sur- 

 face of the wing into small, irregular polygonal areas or 

 cells. The vein nearest the anterior or costal margin (c. m) 

 of the wing is thccostalvein, (c. v). It is undivided and may 

 be traced for a little more than half the length of the wing. 

 The second very much larger vein isthe sub-costal {sub.c.v). 

 It gives rise to several large branches, the subdivisions of 

 which form the framework of the greater part of the 

 wing. The third or median {m. v) is much smaller and 

 soon divides into two branches of nearly equal size. The re- 

 maining pair, which are known as the sub-median, [sub. m. v) 

 and internal (/. v), run close to and parallel with each 

 other near the internal or posterior margin of the wing. 

 The tegmina is divided by these veins into three areas. The 



Fig. 34.— Wing oi Melanophis bivittatus. Original. 



costal area forms the anterior edge of the wing and is 

 bounded posteriorly by the costal vein ; the median area is 

 much the largest, and lies between the sub-costal and sub- 

 median veins; the internal area is the free margin posterior 

 to the internal vein. The second or lower pair of wings, 

 (Fig. 34), are about equal to the first in length, and when 

 the animal is at rest, are folded up under the latter. If the 

 dark-colored marginal vein of this lower wing is gently 



