— 8 7 - 



The following are some of the more important points to be 

 noted in the descriptions : The extent of vein I. The ex- 

 tent of vein II. The number of branches of vein III ; in 

 this connection determine which of the radical cells has been 

 obliterated by the coalescence of branches of vein III. The 

 position of the cross-vein III-V ; the number of branches of 

 vein V ; the division or not of cell V2 ; the presence or ab- 

 sence of cell V3 ; the courses of the branches of vein VII2 ; 

 and the course of vein IX. 



Wing of Protoplasa. — Study the figure of the wing of 

 Protoplasa fitchii (Fig. 9) as an illustration of a wing in 

 which radius is five-branched. Do not be confused by the 

 spur at the base of vein III2+5 (marked ^ in the figure) ; 

 this is a secondary development. 



ix-vfiT - vn ' 



Fig. 9. — Wing of Protoplasa fitchii. 



Wing of a Leptid. — A specimen of one of the snipe- 

 flies, Leptidce, will be given the student for examination with 

 a hand lens. Note the deep furrow between veins I and III ; 

 along the bottom of this furrow vein II extends. Vein II, 

 therefore, is a concave vein. Note that this corrugation 

 stiffens the wing. It is along the costal edge that the wing 

 needs to be strongest, and correlated with this fact we find 

 that vein II is usually a concave vein. 



Make a drawing of a mounted wing of one of the Leptidce. 

 Note that in the mounted specimen vein II is more or less 

 concealed by vein III, although the two veins are distinct, 

 as was seen on the unmounted specimen, studied with a 



