[ntroduction. 



9 



advantageous that by chiefly using well known terms we may avoid un- 

 necessary confusion and at the same time be capable without difficulty 

 to bring the wings of the Diptera under a general point of view. — 

 The terminology used is the foUowing: 1. the costal vein, stopping 

 near the apex or extended all round, 2. the niediastinal vein which 

 is concave, 3. the subcostal vein, convex, 4. the radial vein, concave, 

 5. the cubilal vein, convex, 6. the discai vein, concave, 7. the postical 

 vein, convex, 8. the anal vein, concave, 9. the axillary vein, convex. 



Fig. ->, 



Wing of Tiihatms fropicus. 



The cells are: a, the costal cell, b, the niediastinal cell, c, the sub- 

 costal cell, d, the cubital cell, e, the discai eell, f, posterior cells, 

 g, the first basal cell, h, the second basal cell, i, the anal cell, and 

 k, the axillary cell: x is the medial cross-vein, y, the postical 

 cross-vein. 



Fig. 3. Wing of Dexia canina. 



The niediastinal vein is generally near to the base connected 

 with the costal vein by a cross-vein, the basal cross-vein, and then 

 there are two costal cells. The radial vein is often unbranched, but may 

 be branched, and then there is more than one subcostal cell; the 

 subcostal cell or cells lie between the convex subcostal vein and the 

 concave radial vein, or between the branches of the latter. The cubital 

 vein is generally branched and there may be up to three cubital cells; 

 the cubital cells lie between the concave radial vein and the convex 



