66 VENATION. 



transverse vein is bent downwards in such a way as greatly to 

 narrow the basal half of the discal cell, the width of the distal 

 portion of the anterior basal cell being correspondingly increased ; 

 the fourth vein bends abruptly upwards to the point of contact 

 with the anterior transverse vein, where it forms with itself 

 what is practically a right angle ; from this point it again runs 

 obliquely downwards, and is once more bent upwards at the 

 exact point of contact with the posterior transverse vein, 

 ultimately reaching the margin of the wing some distance before 

 the apex. The first posterior cell is open, but its distal por- 

 tion is narrow and much drawn out. The third longitudinal 

 vein is very close to the second, and shows a marked approxi- 

 mation to the costa, the sub-marginal cell being correspondingly 

 narrow ; the third costal cell is considerably elongated ; the 

 second, third, and fourth longitudinal veins all tui'n upwards at 

 the tips, and the anterior transverse vein is very oblique ; the sixth 

 longitudinal vein becomes obsolete soon after the anal cell, 

 though in clear, unchitinised form it can still be traced nearly 

 to the margin of the wing. Posterior basal transverse vein, 

 closing the anal cell, angulate in the middle, so that the distal 

 angles of the cell are acute. Posterior transverse vein slightly 

 curved, bent up somewhat abruptly to meet the fourth longi- 

 tudinal. Wings of an uniformly brownish hue, varying in 

 intensity in the difierent species, but apparently palest in 

 01. morsitans ; membrane of the wing rilled.* 



[Besemhlance in venation between Glossina and Hypoderma.—- 

 While there are many noticeable differences, the venation of 

 the wing of Glossina resembles that of the (Estrid Hypoderma 

 (Warble-flies) more closely than that of any other genus, especially 

 as rewards the shape of the first posterior cell. In both cases the 

 fourth vein is bent up to form what German authors call a 

 ^^ Spitzenquerader" precisely at its junction with the posterior 

 transverse vein. But in the wing of Hypoderma the anterior 

 transverse vein is not oblique, and the fourth longitudinal vein 

 before reaching it is not bent down in the manner so characteristic 



* Cf. Garry de N. Hough, M.D., " Some Muscinse of North America," 

 " Biological Bulletin," Vol. I. (1899), p. 20, note 1 : — " These rills are very 

 fine grooves in the surface of the wing, which run in a sort of radiate 

 manner towards the border. They are very numerous. A rilled wing 

 denotes a higher stage of development, a more recent form, than an 

 unrilled wing." 



