Subfamily Leptogastrinae 



These asilids comprise a relatively small group of 

 flies, even though the genus Leptogaster Meigen is 

 nearly world wide in distribution and contains a very 

 large number of species. They are rather readily char- 

 acterized by the long, quite slender, somewhat clubbed 

 or clavate abdomen and especially by the complete lack 

 of pulvilli, the palpus of one segment and the absence 

 of the alula. All these characters are collectively found 

 in Leptogastrinae, but are singly shared by other 

 asilids. The empodium is occasionally wholly absent 

 or rudimentary and in one genus the medial claw has 

 become shorter and smaller than the lateral claw. 

 Some delicate species measure as little as 6 to 8 mm. in 

 length ; others reach a length of 33 mm. 



A surprising development appears in the bizarre 

 Central American genus Eurhabdus Aldrich, where the 

 whole basal half of the wing is reduced to a single, 

 stout stalk. The palpus in Leptogastrinae has a distinc- 

 tive form and consists of one segment with sometimes 

 a more or less fused rudiment of the basal segment; its 

 form is cylindroid and clavate. The venation of 

 Leptogaster Meigen sensu stricto is quite variable and 

 in the subfamily as a whole two trends are evident: in 

 one generalized group the anal cell remains open, some- 

 times to an exceptional and marked extent ; in another 

 group of genera the anal cell is closed with a long 

 stalk and the elongate hind femur and tibia tend to 



become swollen either with or without dense hair 

 brushes. 



Although some authors have removed Acronych.es 

 Williston from the Leptogastrinae to the Dasypogon- 

 inae, its correct position is here in this subfamily and 

 these flies have a characteristic f acies. I would regard 

 this subfamily as most closely allied to the 

 Dasypogoninae. 



Some rather interesting general similarities exist 

 between the Leptogastrinae and certain delicate, slender 

 members of the Ehagionidae, as well as certain tipulids ; 

 some East Indian tipulids posess venation strongly 

 resembling Leptogastrinae and still further possess the 

 strong neuromarginal setae seen on radius and medius 

 in Schildia Aldrich. 



Certain species are frequently found in the herbage 

 associated with forests, but others occur in grassland. 

 For larval habits see Malloch, 1917, and Melin, 1923. 



As far as is known, this subfamily dates back to the 

 Oligocene and Miocene; 3 fossil species have been de- 

 scribed, 1 from the Florissant, Colorado beds, and 1 

 from Radoboj, Croatia, and 1 from Camoins, France. 

 While the Asilinae and the Dasypogoninae date back to 

 the Eocene, only 12 fossil asilids have been described 

 from both Eocene and Oligocene. These are so few, 

 in fact, that statistically their numbers would not rule 

 out the likelihood that Leptogaster Meigen may also 

 date back further. 



KEY TO GENERA OF LEPTOGASTRINAE 



1. Anal part of wing greatly reduced ; only 3 posterior cells 



present and the discal cell absent. Prehumeral part of 

 wing greatly lengthened and forming a stalk equivalent 

 to fully half the total wing length; eyes beneath the 

 highly placed antenna completely holoptic. Abdomen very 

 long and exceedingly slender; halteral stalks exception- 

 ally long with prominent, clubbed discs; empodium well 



developed Eurhabdus Aldrich 



Anal area of wing developed even though narrowed . 2 



2. Only 4 posterior cells and only 1 anal cell present. 



Leptopteromyia Williston 

 Five posterior cells and 2 anal cells present .... 3 



3. Anal cell open and usually widely open 4 



Anal cell closed and usually with a long stalk .... 15 



4. Prothorax medially with a short, distinct protuberance. 



Hind femur rather swollen, attenuate only on the basal 

 third or less, the tibia unmodified. Third antennal seg- 

 ment spindlelike and always 2 times as long as the first 

 two segments combined. Mesonotum and pleuron in part 

 with dense, flat-lying pile ; empodium absent or rudimen- 

 tary Euscelidia Westwood 



Pronotum without such protuberance 5 



296 



5. Radial and medial veins margined on either side with regu- 



larly spaced, long, conspicuous setae. Third antennal seg- 

 ment laterally compressed and attenuate basally, its dor- 

 sal apex with a short or long style or bristle. Anal cell 

 widely open. Empodium absent; medial claw shorter 

 than lateral claw (including Shannomyioleptus Carrera). 



Schildia Aldrich 

 These veins with only the usual dense, minute micropubes- 

 cence; third antennal segment sometimes a little narrowed 

 at base, but attenuate distally, the style well devel- 

 oped 6 



6. Empodium completely absent or rudimentary .... 7 

 Empodium well developed 10 



7. Front strongly divergent downward, and below the antenna 



the divergence of the face is continued even more strongly, 

 so that the face above the epistoma is unusually wide. 

 Third antennal segment 2 or 3 times as long as the com- 

 bined length of the first two segments, stout, greatly 

 tapered toward the apex and bearing a quite short, 

 swollen style. Face prominent, as wide as high, with a 

 few, fine hairs and the mystax confined to a transverse 

 row of bristles along the epistomal margin. Anal cell 

 closed in the margin .... Acrontches Williston 



