L^PTIDM 239 



4 Submarginal cell. 



4=' Second submarginal (or cubital) cell (or mhital forh-cell). 



5 First posterior (or svhajnccd) cell. 



6 Discal cell. 



6=^ Second posterior cell. 

 6'' Third posterior cell. 

 6" Fourth posterior cell. 



7 Postical (or 5th posterior) cell (or postical fork-cell). 



8 Axillary cell. 



9* Upper (o?- IsO basal cell. 

 9^ Second (or middle) basal cell. 

 9" Anal (or 3rd basal) cell. 

 10 Alula. 



Notes on the Venation of the Leptid^. 



The venation in the various subfamilies exhibits a transition from the Stratio- 

 myidce to the Tabanidce. In the Xylophagince it is almost identical with that of 

 ttie Xylomyinoi, but two important distinctions exist ; in the Xylom^jincB (as in 

 all the Stratiomyidce) the ambient vein is incomplete even though it may extend to 

 the end of the second veinlet from the discal cell, but in the Xi/lojjhagince (as in all 

 the Leptidce) the ambient vein though faint is complete ; the peculiar fork of the 

 cubital vein, common to the Xylomyince and Xylo2}hagince, is seen no more in the 

 Brachycera, but the closed fourth posterior cell re-occurs in Lampromyia and 

 becomes common in the Dermatina and Eremoch.eta only to die out again after 

 the Asilidoe.. 



The Pr^fueca always starts well before the base of the discal cell. 



The Cubital Vein is connected soon after leaving the radial vein with the discal 

 cell on the basal third of the cell (whenever the cell exists) by the discal cross-vein. 

 It is always forked and in the tyj^ical Leptiiup the fork is long and more or less 

 bell-mouthed but hardly more open than the first posterior cell ; it begins almost 

 opposite to or before the end of the discal cell and has the upper branch ending 

 almost in the wing-tip, but in other subfamilies the fork is of a varied nature ; as 

 mentioned above, in the Xylophagince (fig. 182) it is almost identical with that 

 of the Xylomyinoi and its long lower branch ends almost in the wing-tip ; in the 

 Vermileonince (fig. 184) it is wide open and includes the wing-tip in an equilateral 

 triangle but yet is only moderately suggestive of the 'fabanidw ; in the Coenoviyince 

 (fig. 186) it includes the wing-tip at the end of a long bell-mouthed fork ; in Ptiolina 

 and Spania the whole fork is above the wing- tip because the lower branch ends almost 

 in the wing-tip \ and in Ifilarimorpha (fig. 1 77) it is short and wide open but is mainly 

 above the wing-tip. The character of the Discal Cross-vein being placed on the 

 basal third of the discal cell helps to distinguish the Leptidce from the Asilidce and 

 Therevidce, though it is not an invariable character. 



The Discal Cell (when present) is always elongate and hexagonal (on the 

 assumption that there are three angles at its base and three at its end). In the 

 tyi^ical subfamilies the Small Cross- vein is well defined, but in the Xylophagince it 

 is almost absent, and in Coenom]/ia the upper branch of the postical vein forms for a 

 long distance the lower margin of the discal cell. The discal cell always emits three 

 veinlets (irrespective of the upper branch of the postical vein) and consequently there 

 are always five posterior cells (except in Hilarimorpha, which also has no discal 

 cell). 



The Postical Vein is as simple as possible in the genus Leptis, but in other 

 genera tho lower branch very commonly joins the anal vein at or near the Aving- 

 margin and thereby forms a closed anal cell, and the upper branch as mentioned 

 above sometimes touches the discal cell and in Coenomyia forms the under side of 

 that cell for a long distance. 



The Ambient Vein is always complete even though sometimes faint, and this 

 character gives an unfailing distinction from the allied subfamilies of Stratiomyidce. 



There are other peculiarities in the venation of the Vermileonince (vide p. 257). 



