1 8 DUBHAM DIPTEEA. 



(C.II.4.) V.3. It springs from the hinder side of V.2., or from 

 V.I. if V. 2. be absent. It is always present, 

 and is always the lowest long vein of the front 

 vein-system ; that is, it is always the first vein 

 above the ordinary cross-vein, X.4. 



V.4. It springs from the upper side of V.5., and is the 

 uppermost long vein of the middle vein- 

 system. It is often much branched and 

 sometimes absent. 



V.5. The main strong vein of the middle system. 



V.6. It springs from the under side of V.5., and it is 

 often weak or absent. 



V.7. The last vein. It springs direct from the root 

 of the wing. It is generally weak, and often 

 absent. 



The veins are divided into sections by the 

 X-veins and the branches. These are in- 

 dicated by small numbers placed above the 

 line. For instance, in the chart, V.4 1 would be 

 the portion of V.4. from its base to where it is 

 met by X.5 1 ; V.4 2 the portion from X.5 1 to X.4 ; 

 V.4 3 from X.4. to X.5 2 ; V.4 4 from X.5 2 to the 

 margin. If V.4. happened to branch as in the 

 dotted line, V.4.b. then V.4 2 would be the 

 portion from X.5 1 to the fork, and the re- 

 mainder of what was V.4 2 would become 

 V.4.a\ that is, the first section of the upper 

 branch of the fourth vein, and so on. 



Vena Spuria. — A longitudinal thickening of 

 the wing, characteristic of the family Syrphidae. 

 It looks like a vein lying between V.3. andV.4., 

 and crossing X.4., after which it dies away. 

 (See the dotted line in Plate V.19, 20, 21). 



(5) The Cross Veins. — These are short veins connecting 

 the longitudinal veins. 

 X.I .a. Near the base of the wing in front. 



