542 THEREVID^ 



6 Discal cell. 



6'' Second posterior cell. 

 Q^ Third posterior cell. 

 6" Fourth posterior cell. 



7 Postical (or bth 2)osterior) cell {or postical forh-cell). 



8 Axillary cell. 



9» Upper {or Ist) basal cell. 

 9^ Second {or middle) basal cell. 

 9" Anal {or lower ^ or 3rd banal) cell. 

 10 Alula. 



Notes on the Venation of the Tiierevid^.. 



The venation is very simple and liable to very little variation. 



Subcostal Vein short, thereby affording a distinction from the Asilidce and 

 Apioceridce. PRiEFUECA rather long, starting before the middle of the upper basal 

 cell and consequently far before the base of the discal cell. Discal cross-vein 

 placed near the middle of the discal cell, and consequently the upper basal cell 

 longer than the second. Cubital Fork wide open and including the wing-tip, but 

 not so wide open as in the Tahanidce, and usually the upper branch ending as far 

 from the radial vein as from the lower branch ; the cubital fork starts after the end 

 of the discal cell. Discal Cell hexagonal and emitting three almost equidistant 

 veinlets, of which the lower one is usually bent down and sometimes closes the 

 fourth posterior cell. Posterior Cells always five, the fifth (postical) having its 

 upper vein sometimes connected at the wingmargin with the third veinlet from the 

 discal cell, and its lower vein always connected with the anal vein. Small cross- 

 vein always distinct. 



Table of the Palcearctic Genera of Therevid^. 



1 (6) Basal antennal joint almost as long as (or even longer than) the 



head. Species almost bare. 



2 (3) Basal antennal joint long and thin, antennae twice as long as 



the rather short head. 



Fourth posterior cell closed. Abdomen elongate, pointed. 



Phycus. 



3 (2) Basal antennal joint remarkably thick, much longer than the 



other two together; antennse hardly longer than the rather 

 long head (fig. 313). 



Fio. ZXZ.— Xestowijza chrysantliemi ?. x 24. 



4 (5) Eyes of the male separated. Basal antennal joint bristly from 

 hase to tip (fig. 313). 



Discal cross-vein near the middle of the discal cell. 



Xestomyza. 



