324 TABANID.E 



5 First posterior {or suhapical) cell. 



6 Discal cell. 



6=' Second posterior cell. 

 6"' Third posterior cell. 

 6" Fourth posterior cell. 



7 Postical {or 5th jwsterior) cell {or 2)ostical fork-cell). 



8 Axillary cell. 



9^ Upper {or 1st) basal cell. 

 9^ Second {or middle) basal cell. 

 9" Anal {or Srd basal) cell. 

 10 Alula. 



N'otes on the Venation of the Tabanid^. 



The most characteristic features in the venation of this family lie in (1) the 

 prsefurca and its origin ; (2) the cubital fork ; and (3) the small cross-vein. 



(1) The Pr^fueca always starts from the subcostal vein far before the base 

 of the discal cell, and is always long. 



(2) The Cubital Fork is very characteristic and in itself Avill almost always 

 allocate a species to this family, though a few aberrant Leptidce { Vermileonince) and 

 some Bomhylidce have a somewhat similar fork. The Fork is very wide open 

 triangularly, with the upper branch rather longer than the lower one and ending 

 well before the wing-tij^, while the lower branch ends considerably more than that 

 distance after the wing-tip ; normally the upper branch ends rather near the radial 

 vein and about as far from it as the lower branch does from the upper veinlet from 

 the discal cell, and the ivingmaryin included between the branches of the fork is 

 mam/ times longer than that of the adjoining cells, but the upper and lower veinlets 

 from the discal cell often vary until the uppermost one may connect before the 

 wingmargin with the lower branch of the cubital fork, and the lowest veinlet 

 from the discal cell may connect in a similar fashion with the u^jper branch 

 of the postical fork. The Fork begins after the end of the discal cell, and the upper 

 branch often emits a short recurrent veinlet (as in many Bomln/lidce) from the 

 angle soon after its base, but this character is of only minor specific value as it is 

 not constant. 



(3) The Small Ckoss-Vein is always present, and that character combined with 

 the five posterior cells gives an infallible distinction from the Bombj/lidce. 



Other details worthy of note lie in the complete Ambient Vein, the long hexagonal 

 Discal Cell with the Discal Cross-Vein placed on its basal third almost opposite to the 

 (always present) Small Cross-Vein, and the well-developed Alula. 



TaUe of the Palmarctic Genera of Tabanid^e. 



1 (6) Hind tibiae without any spurs. Ocelli often absent. 



Tabanin^ (p. 327). 



2 (3) Third antennal joint not dilated nor dorsally humped near its 



base nor with any style-like termination, but apparently 

 divided into a long simple cylindrical basal and three shorter 

 apical joints (fig. 212). Hexatoma. 



3 (2) Third antennal joint dilated soon after its base and often dorsally 



humped there (fig. 214), and with three or four subsequent 

 annulations which are hardly separable into joints. 



4 (5) Wings grey with hyaline dots indicating numerous imperfect 



ocelli (fig. 222). Third antennal joint dilated near its base 

 but not dorsally humped there (fig. 213), and with three 

 subsequent annulations. Frons of the female as broad as, or 



