most about one and a half times. In LEPTID^E the discal cell is 

 distinctly oblong and always more than twice as long as wide. 

 The only two genera about which doubt might arise would be 

 Xylophagus and Xylomyia* The TABANID^E, though possessing 

 the same venation as the LEPTIDTE, may at once be recognized 

 by the characteristic antennae and their more robust structure 

 throughout. 



Table of Subfamilies. 



1. Third antennal joint flagelliform, more or less 



elongate, simulated, without arista 2. 



Third antennal joint not flagelliform, short, or 

 but little elongated, rounded, conical, or 

 reniform, never distinctly annulated ; arista 

 always present 4. 



2. All tibiae with spurs , 3. 



Front tibiae without spurs ARTHROCERATIN^E. 



3. The 5th posterior cell in broad contact with 



discal cell ; face with rounded socketed 

 epistoma, margined by broad side-cheeks ; 

 eyes in c? contiguous ; scutellum with two 



short blunt spines COENOMYTX.S:. 



The 5th posterior cell not touching discal cell ; 

 face flat, epistoma not socketed or margined 

 by broad side-cheeks ; eyes in c? well sepa- 

 rated; scutellum unarmed XYLOPHAGIN^E. 



4. Eyes in $ wide apart ; 3rd vein widely forked 



at much beyond half its length ; face not at 



all socketed VERMII.EONINA:. 



Eyes in <$ contiguous ; 3rd vein less widely 

 forked before, or at latest at, half its length; 

 face with rounded socketed epistoma LEPTIN^;. 



In few families of Diptera is there such diversity of opinion 

 with regard to the subfamilies as in the present one. Prof. Kertesx, 

 in his ' Catalogue of Diptera,' admits none at all, but ranks 

 XYLOPHAGIDJE (including Xylomyia and CCENOMYIJ)^;) as separate 

 families. Verrall recognises the four last subfamilies presented 

 here with CHHYSOPILIN^E as a fifth ; Williston divides the LEPTIDJ- 

 into three (dealing with North-American species only), XYLO- 

 PHAGINJE (including Ccmomyia], ARTHROCERATIN;E (including 

 Xylomyia), and LEPTIN.E. Beling has shown the affinity between 

 Ccenomyia and Xylophagus in their larval stages. 



Verrall divides the XYLOPHAQIN^E and VERMILEONIN^E, taken 

 together, from the C<ENOMYIN,E and LEPTIN*; (with CHEYSOPILIN.T: 

 as an additional subfamily), taken together, by the characters of 

 the face, afterwards distinguishing those of each group from one 

 another by antennal characters ; but the system herein presented 

 is adopted on account of less indecision being likely to arise as to 

 the nature of the antennas than the degree of prominence of the 

 face 



The ARTHROCERATINJE as a subfamily are rather difficult for me 

 to judge personally, since no example is available for actual 



* See XvLOPHAGiNjE (p. 104) and Xylomyia (p. 96) respectively. 



