BRITISH FLIES 13 



15 (10) Subcostal vein unusually long, and often receiving the radial 



vein before its tip. Fourth posterior cell frequently closed. 

 Stigma absolutely absent. XII. Asilidj*:. 



16 (9) Posterior cells four or three. Cubital fork (when present) 



usually large and triangularly wide open, including the 

 wing-tip. VII. BombylidtE. 



17 (8) Discal cross-vein absent in British species; but when present 



placed close to the base of the discal cell, and the continuation 

 of the cell beyond it closed l)y another cross-vein near 

 (sometimes beyond) the end of the discal cell. Venation in 

 British species very much reduced. VI. Cyrtid^. 



18 (3) Upper branch of the discal vein ending before the wing- tip. 



19 (20) Venation very much reduced. IX. Scenopinid^. 



20 (19) Venation elaborate. Veins near the wing-tip upcurved. 



XI. APIOCERIDyE. 



21 (2) Posterior cells (at least the first and normal fourth) with their 



lower margin running parallel with the wingmargin. Discal 

 cross-vein near the end of the discal cell. 



22 (23) Subcostal vein moderate in length and ending simple. " Diagonal " 



vein present. V. Nemestpjnid.^^:. 



23 (22) Subcostal vein remarkably long and receiving subsequent veins. 



" Diagonal " vein not present. X. Mydaid^. 



24 (1) Basal cells or at least the anal cell short, and (except in 



Hylotiiuv) with the lower branch of the postical vein re- 

 curved so that the anal cell ends in an upper point, or the 

 anal or second basal cell absent. Posterior cells four or less. 

 Alula absent. 



25 (28) Venation showing at least one apparent cross-vein well out on the 



disc of the wing. Wings rounded at the tip. 



26 (27) Basal cells usually long enough to be conspicuous. Eadial and 



cubital veins diverging at about one-third the length of the 

 wing. Cubital vein often forked. XIII. Empid/k. 



27 (26) Basal cells very short or obsolete. Padial and culjital veins 



diverging close to the base of the wing. Cubital vein never 

 forked. XIV. Dolichopodid^'r. 



28 (25) Venation abnormal and not showing any apparent cross-vein out 



on the disc of the wing. 



29 (30) Radial and cubital veins long and almost parallel, diverging close 



to the base and ending almost at the wing-tip. Wing-tip 

 pointed. XV. Lonchopterid^. 



30 (29) Ptadial and cubital veins forming one strong vein which extends 



up to near the middle of the costa, and close to which they may 

 diverge ; subsequent veins faint and apparently arising from 

 this prtefurca. Wing-tip rounded. XVI. Phorid/E. 



