WINGS. 39 



cell is bounded in front and internally by the anterior 

 branch of the fifth vein, bordering the discal and basal 

 cells, posteriorly by the posterior branch of the fifth, 

 often also superfluously called the posterior intercalary 

 vein ; this cell in other flies often borders on the discal 

 cell alone internally; tio& fifth posterior cell is bounded in 

 front by the posterior branch of the fifth vein, internally 

 by the petiole of the fifth vein, posteriorly or internally 

 by the posterior basal cross-vein. There is much doubt as 

 to whether this latter is really a cross-vein in the more 

 evident meaning of the word, or whether it really repre- 

 sents the primary branch of the fifth vein, since in man)' 

 flies this is the only termination of the vein, the anterior 

 branches being wholly wanting. The short vein which 

 separates the discal cell from the second basal cell is often 

 called the anterior basal cross-vein; sometimes the discal 

 cross-vein, which would be the better term, were it not to 

 be confused with the posterior cross-vein itself. Follow- 

 ing the third longitudinal vein outwardly it will be found 

 to give off an anterior branch, which runs forward to ter- 

 minate in the anterior marginal vein of the wing, the 

 costa; the cell included in this fork, between the branch 

 and the vein itself is called the second submarginal cell, 

 and this name should always be restricted to the cell so 

 bounded, though usually the cell enclosed between the 

 branches of the second longitudinal vein in the Culicidae, 

 Tipulidse, etc., receives this name. The second longi- 

 tudinal vein borders the first submarginal cell in front 

 and terminates in the costa, as the encompassing vein of 

 the wing is called ; in a relatively few flies this vein also 

 gives off a branch in front, dividing the marginal cell 

 just as the submarginal cell is divided in Tabanus. Be- 

 tween the first longitudinal vein, which has a similar 

 course to that of the second longitudinal, though shorter, 

 and the vein in front of it, between it and the costal bor- 



