LEFTOGASTRINAE 



ROBBER FLIES OF THE WORLD 



297 



Front convergent or at least with the sides parallel; face 

 moderately divergent below. Anal cell widely open. 

 Style of antenna long and slender 8 



8. Basal part of wing greatly narrowed; a complete comple- 



ment of cells present ; wing lanceolate in shape ; anal cell 

 very widely open. Antennal style nearly as long as the 

 third segment, thick and swollen, except at base and spine- 

 tipped ; proboscis exceptionally robust. Fusion of third 

 branch of niedius and first branch of cubitus veins ex- 

 tensive ; occiput prominent. Distal half of hind tibia and 

 first 3 tarsal segments with a dense, conspicuous fringe 



of long, stiff pile Dolichoschts Janssens 



Wing oval in shape, the basal part not narrowed ... 9 



9. Empodium completely absent ; hind femur conspicuously 



swollen distally, the tibia stout, except near the 



base Psilontx Aldrich 



Empodium rudimentary ; hind tibia more or less dilated in 

 the middle ; apical segment of hind tarsus thick, swollen, 

 convex Sinopsilontx Hsia 



10. Hind femur gently swollen from the base and bearing dense 



pile on all surfaces, subappressed laterally, erect else- 

 where. Hind tibia without conspicuous pile but with 4 

 or 5 stout, dorsal bristles and 2 or 3 ventral bristles. 

 Margin and disc of scutellum with considerable, long 

 coarse hairs. Wings with diffuse spots or bands. Sides 

 of lateral metasternum not encroaching behind the coxae, 

 the postmetacoxal area membranous. 



Systellogaster Hermann 



Hind femur not swollen and hirsute as described above. 



Wings without spots or bands 11 



11. Third antennal segment relatively short, the base swollen, 



the apex narrowed and attenuate ; style of varying length. 

 Hair flocks never present on the middle of the inner side 

 of the hind femur. Face usually protuberant below but 

 plane with the eye margin above 13 



Third antennal segment relatively elongate, drawn-out, 



slender and tapered 12 



32. Hind tibia laterally with only 1 bristle at middle and 1 

 at apex Ttpulogaster Cockerell 



Hind tibia with a series of more or less stout bristles. 



Mesoleptogastee Frey 



13. A median band of hairs on second abdominal tergite. First 



and second sternites narrow or obsolete, if present, fused 

 to second tergite. Anterior intercalary vein sharply 

 angulate. Empodium present. The superior forceps 

 usually tapered to a point (subgenus of Lcptogaster 



Meigen) Beameromyia Martin 



Without a median band of hairs on second abdominal 

 tergite. Anterior intercalary vein usually straight, but 

 not in all species 14 



14. Hind femur long, but little swollen or dilated distally; legs 



generally rather long. Female ninth tergite notched, 



resulting in 2 narrow, lateral lobes (subgenus of Lcpto- 

 gaster Meigen) Apaciiekolos Martin 



Hind femur relatively more swollen. Ninth tergite not 

 notched Leptogaster Meigen 



15. Hind femur, tibia or both swollen and dilated .... 16 

 Hind femur or tibia not conspicuously thickened, dilated 



and swollen. Hind femur with a medial flock of long 

 hairs near the middle 20 



16. Prothorax medially with a short, distinct protuberance. 



Hind femur rather swollen; hind tibia simple. 



Euscelidia Westwood 

 Prothorax without medial protuberance 17 



17. Empodium absent. Third antennal segment large, long, 



stout and tapered, the style short and stout .... 18 



Empodium present, usually nearly half as long or more 



than half as long as claw i;i 



18. Front divergent from the vertex downward ; length of face 



more than half the length of the subfacial sclerites ; pile 

 of face limited to a few, fine, scattered hairs. The mystax 

 reduced to a transverse row of a few (3 pairs) stout 

 bristles placed midway between antenna and proboscis. 

 Hind femur with a limited, distal band of hairs on medial 

 surface only. Medium-size flies . Acronyches Williston 

 Front slightly divergent. Face very short, little more than 

 a third the length of the subfacial sclerites and with a 

 medial tuft of long, stout, ventral bristles and numerous, 

 slender bristles and bristly hairs reaching to the antenna. 

 Hind femur with a dense brush of long, coarse hairs on 

 dorsal and medial surfaces confined to the outer, swollen 

 half of femur. Very large flies . . Megontx, new genus 



19. Hind femur swollen, tibia simple. Hind femur dorsally 



with a prominent, complete brush of long, dense pile, the 

 ventral surface with a similar brush on the distal half; 

 third antennal segment very long, more than 2 times as 

 long as either the basal segments combined, or the style. 

 Face reduced in length ; mystax reduced and petiole long ; 



wings dark Ophionomima Enderlein 



Hind femur and tibia both swollen and with complete dorsal 

 and ventral brushes of long, dense pile. Wings often 

 maculate with pattern of clear areas, or wholly dark; 

 antennal style approximately as long as the third seg- 

 ment LASiocNEMrs Loew 



20. The discal cell ends with a single, rectangular crossvein. 



which is the medial crossvein ; the anterior branch of 

 the fourth vein forks far toward the base of the wing. 

 The prosternum is fully and widely united to the lateral 



propleuron Ammophilomisia Enderlein 



The upper anterior portion of intercalary vein is very little 

 longer than the medial cross vein and in consequence the 

 anterior branch of the fourth vein forks close to the 

 medial crossvein. Prosternum with a distinctly broken 

 or greatly reduced connection to the lateral proster- 

 num Lagykogaster Hermann 



Genus Leptogaster Meigen 



Figures 200, 202, 590, 591, 598, 606, 1175, 1183b, 2242, 2278 



Leptogaster Meigen, Mag. Insektenkunde, vol. 2, p. 269, 1803. 



Type of genus : Asilus cylindricus De G6er, 1776, as Asilus 



tipuloides Fabricius, 1775, by monotypy. 

 Gonypcs Latreille, Histoire naturelle . . . des insectes, vol. 14, 



p. 309, 1805. Type of genus : Asilus cylindricus De Geer, 



1776, as Asilus tipuloides Fabricius, 1775, by monotypy. 



Engel (1925) gives 1776 for date of Asilus tipuloides; 

 Kertesz (1909) gives 1775 for this date. If the latter 

 date holds, then Asilus tipuloides is a good species and 

 Asilus cylindricus is a synonym. 



Leptogaster has 2 subgenera, ApacheJcolos Martin 

 and Beameromyia Martin. 



Slender, elongate flies with slightly clavate abdomen 

 and elongate hind legs. The palpus has only one seg- 

 ment and is of characteristic, clavate form with blunt, 

 obtuse, rounded apex. The alula is absent and the 

 face strongly divergent. Moreover, the pulvilli are 

 always lacking and all wing cells open widely, including 

 the anal cell. Length 5 to 30 mm., these extremes being 

 uncommon. 



Head, lateral aspect: The head is medium length, 

 the face slightly produced on the lower fourth, always 

 plane with the eye beneath the antenna and sometimes 



