NO. 12 FLYING APPARATUS OF BLOW-FLY RITTER 1 3 



I shall now describe the eight longitudinal veins. 



Gi, the marginal vein (text fig. 2 ; pi. 5, figs. 15, 17 ; pi. 8, figs. 23, 

 24, gi), begins with a clnb-shaped swelling at the processus pteralis 

 alas I. It is notched in the flexible zone (vide infra), and extends, 

 gradually diminishing in thickness, as far as the medio-marginal 

 transverse vein of Lowne (text fig. 2 ; pi. 5, figs. 15, 17, gj. 



The four following veins are joined basally to a single vein, the 

 remigium (text fig. 2; pi. 5, figs. 15, 17; pi. 8, figs. 23, 24, re), 

 which appears as a short and very strong tube. The remigium is 

 the strongest vein of the entire wing. 



laa, the auxiliary vein (mediastinal) (text fig. 2; pi. 5, figs. 15, 

 17; pi. 8, figs. 23, 24, laa) arises at the point where the anterior 

 transverse vein (at) touches the remigium. Basally, in the flexible 

 zone, it exhibits a transverse striation (vide infra). 



Iba (subcostal) (text fig. 2; pi. 5; figs. 15, 17; pi. 8, figs. 23, 

 24, Iba) arises from the remigium and is about its middle strength- 

 ened by a swelling. 



Ilaa (radial) (text fig. 2; pi. 5, figs. 15, 17; pi. 8, fig. 23, lllaa) 

 and 



Illba (ulnar) (text fig. 2; pi. 5, figs. 15, 17; pi. 8, fig. 23, Illba) 

 arise together from the remigium. They are connected with the 

 latter by a piece which exhibits particularly clearly the transverse 

 striation of the veins in the flexible zone (pi. 7, figs. 20, 21, 22). 

 The place of common origin of these two veins is thickened and set 

 with bristles. Between these two veins there are two high folds, 

 one projecting upward (convex), Ilba, the other projecting down- 

 ward (concave), Illaa. 



lam. Discoidal vein (median) (text fig. 2; pi. 5, figs. 15, 17; 

 pi. 8, figs. 23, 24, lam) . This is the first vein of the median area ; 

 it forms, with the Ilbm and the transverse vein of the knee, the knee 

 of the wing (fk). It is connected with Ilba, proximally, by the 

 transverse vein of the knee (patagio-hypocostal), farther on by 

 the median transverse vein (q), and at the tip by the medio-mar- 

 ginal transverse vein q-^ with the end of the marginal vein. Between 

 lam and Illba are found the folds IVaa and the Spuria, IVba. 



Ilbm (siibmedian) (same figs.) extends in the crest of a strongly 

 protruding, convex fold right to the posterior margin of the wing. 

 It arises from the knee of the wing and is connected with /awi by 

 two transverse veins ; the postical transverse (po) and the discoidal- 



