II] 



WING VENATION 



of the latter is of great use in the identification of various species 

 of mosquitoes. The venation, although comparatively simple, 

 has been greatly complicated by the fact that entomologists 

 are not agreed as to the terminology of the various parts and 

 in consequence different writers use different names for the 

 same structures. 



In the following description of the wing of Tabanus, which 

 is taken as an example because the venation is rather compli- 

 cated, we have adopted the system of nomenclature most 

 generally used by descriptive entomologists. 



Auxiliary nerve 



.... . X Subcostal cell 



Anterior cross-vein v ' * 



Cosl"al vein 



Humeral cross-vein 



Posterior cross-vein 



Anterior basal cross-vein 



Fig. 5. Wing of Tabanus sp. shewing the venation. The numbers I, II, 

 III, etc. indicate respectively the first, second and third longitudinal 

 veins, etc. 



The most easy way of recognizing the veins is to commence 

 with the discal cell, which is a large cell situated about the 

 middle of the wing. It is present in the great majority of flies, 

 but is absent in the Culicidae. Anteriorly, the discal cell is 

 bounded by the fourth longitudinal vein, and somewhere along 

 its length will be seen a short connecting vein, the anterior 

 cross-vein. The latter is constantly present in all flies. In 

 front it is connected with the third longitudinal, and behind 

 with that part of the fourth longitudinal that bounds the 

 discal cell. 



H. B. F. 2 



