8.0 MEDICAL ENTOMOLOGY 



corresponding cardinal number. Thus, 3rd R indicates the third radial 

 cell, 2nd Cu the second cubital cell, and so on. 



The form which approaches the urotype the most closely is Phleboto- 

 mus. In the Culicidae and Tabanidae there is rather more concentra- 

 tion of the veins, but in all the Orthorrapha one finds them distributed 

 more or less equally all over the surface. In the Cyclorraphic flies 

 the concentration is marked, and in the Hippoboscidae the posterior 

 half is almost free from veins, those derived from the posterior tracheae 

 having become very much reduced. 



The cross-veins which unite the longitudinal ones are placed and 

 named as follows. The humeral cross-vein connects the costa and 

 subcosta near the base of the wing. The axillary vein, generally thick 

 but short, connects the veins of the anterior set at the insertion of 

 the wing. The radial-median vein connects the fifth branch of the 

 radial vein with the first division of the median vein. The median 

 cross-vein connects the anterior and posterior divisions of the median 

 vein with one another. The median-cubital vein runs between the 

 fourth branch of the median vein and the first cubital. 



The older system of nomenclature is entirely empirical, and can only 

 be applied to the Diptera. In it the veins are numbered and named in 

 order from before backwards. The costa is the vein 

 Nomenclature forming the anterior boundary of the wing, and is often 

 continuous around the apex with the posterior border. 

 The auxiliary vein or the subcosta lies behind it, and turns upwards 

 to join it before reaching the apex of the wing. Then come in order 

 the first, second and third longitudinal veins, arising from a common 

 stem (the anterior trachea of Comstock and Needham's nomenclature), 

 and behind them the fourth and fifth longitudinal veins, arising by 

 a common stem corresponding to the posterior trachea. Behind these 

 there is a sixth, and in some cases a seventh, longitudinal vein, which 

 go to the posterior margin of the wing and correspond to the anal 

 veins. The cross-veins are named as follows. The humeral cross-vein 

 corresponds to that of Comstock and Needham's nomenclature. 

 The anterior, small, or middle cross-vein unites the third and 

 fourth longitudinal veins, the posterior or lower cross-vein the fourth 

 and fifth, and the upper or supernumary cross-vein the second and 

 third. The cells into which the wing is divided are named more 

 or less in accordance with their position. Commencing at the ante- 

 rior border, the costal cell lies between the costa and subcosta. The 

 subcostal cell lies between the subcostal vein and the. first, longitudinal 



