DASYPOGONINAB 



ROBBER FLIES OF THE WORLD 



113 



has only short, stiff pile. Mesopleuron and ptero- 

 pleuron apilose. Upper stemopleuron with 2 or 3 short 

 hairs; posterior hypopleuron with a tuft of short, 

 bristly hairs. Metapleuron with 8 or 10 fine hairs, 1 of 

 which might be described as a slender bristle. Meta- 

 notal slopes pubescent only; lateral metasternum 

 apilose, ventral metasternum chitinized with a band of 

 short pile. Postmetacoxal area membranous; tegulae 

 pubescent only. 



Legs: The femora are rather stout, especially the 

 anterior and middle pair. They are extremely short 

 appressed pilose with few bristles. These bristles and 

 especially those of the tibiae are exceptionally stout. 

 Anterior coxae anteriorly with some 40 bristles; middle 

 coxae with 20; posterior coxae laterally with 3; the tro- 

 chanters with 3. The hind femur has 1 stout, dorsal, 

 subapical bristle and a stout dorsolateral back from the 

 apex ; its tibia has 1 short dorsal, 3 ventrolateral grow- 

 ing progessively longer, and ending in a still longer 

 apical bristle; apex with 1 dorsal, 2 lateral, the lower 

 one exceptionally long and stout, 2 long, stout ventrals, 

 and 1 or 2 medial. Ventrally this femur and tibia are 

 very short, appressed pilose. Middle femur with 2 

 stout posteroapical, 1 anterodorsal at the apical third, 



2 weak dorsal, 2 anteroventral, the last subapical is 

 very long and stout and longer than the basitarsus, be- 

 sides posteroventrally on the outer half 3 exceptionally 

 stout, long bristles. Anterior femur with a small bristle 

 posteriorly near the middle ; its tibia gradually dilated 

 to nearly twice the basal width and it bears 3 postero- 

 ventral, exceptionally long, stout, oblique bristles on 

 the outer half. The hind tibia at apex tends to have 

 one of the apical, ventral bristles directed obliquely 

 downward. All tarsi end in stout, rather pointed claws, 

 long spatulate pulvilli and long, stout empodium. 



Wings: The wings are distinctly shorter that the 

 abdomen, reaching just beyond the fifth tergite. Mar- 

 ginal cell widely open ; the anterior branch of the third 

 vein ends a litte before the wing apex and is gently sig- 

 moid. First posterior cell is fully open; fourth pos- 

 terior cell is closed in the margin or narrowly open; 

 anal cell is closed in the margin. Alula moderately 

 wide, ambient vein complete, second basal cell ends in 



3 veins, the middle vein short. 



Abdomen : The abdomen is slender, gently tapered, a 

 little flattened on the third to fifth tergite. Males with 

 eight tergites, the eighth only one-fifth as long as the 

 seventh. Eight tergites present in the females, the 

 eighth quite short, about one-seventh as long as the 

 preceding one. Pile of abodmen very short setate and 

 subappressed and without long pile laterally. First 

 tergite with 2 or 3 short, weak bristles laterally and 

 a few hairs of about the same length. Abdomen polli- 

 nose laterally, more shining towards the middle, wholly 

 shining on the seventh tergite. Males with moderately 

 large, obtuse, fully cleft and apposed epandrium and 

 small proctiger. Gonopod larger; it is not as long as 

 the epandrium but has greater depth. Hypandrium 

 short but distinct. Males lack the down-turned hood 

 so characteristic of Stichopogon Loew and its allies. 



Female terminalia with 4 or 5 pairs of stout spines 

 laterally. Ventral plate cleft, a few short bristles 

 present. 



Distribution: Nearctic: Willistonina bilineata Wil- 

 liston (1884), bilineata nigrofemorata Wilcox (1935). 



Genus Rhadinus Loew 



Figures 52, 456, 934, 943, 1688, 1970 



Rhadinus Loew, Neue Beitrage . . . pt. 4, p. 38, 1856. Type of 

 genus: Rhadinus ungulinus Loew, 1856. Designated by 

 Engel, 1929. 



Small, slender flies, densely pale pollinose, the base 

 of the abdomen is nearly as wide as the mesonotum but 

 rather strongly tapered. Related to Stichopogon 

 Loew. The face is beset with scalose pile which in some 

 cases is quite broad and striking. The front is exten- 

 sive and with the vertex moderately expanded. They 

 are immediately separated from related genera by the 

 absence of pulvilli; the antennal style tends to be more 

 slender and elongate. Length 6 to 9 mm. 



Head, lateral aspect : The length of the head is two- 

 thirds of the height. The face is visible only very 

 slightly below and visible here because of the natural 

 recession of the eye. It is slightly rounded, convex, 

 retreating and short ; the antenna is placed quite low. 

 The eye is large, long, strongly and rather evenly con- 

 vex anteriorly but with a marked anteroventral reces- 

 sion posteriorly beginning from the middle of the head. 

 The occiput is well developed and prominent on the 

 lower half, short above the middle of the head and en- 

 tirely obliterated near the vertex. The pile of the oc- 

 ciput is abundant, long, coarse, becoming scanty on the 

 upper third and absent above this point, where it is re- 

 placed by short bristles that become longer and stouter 

 behind the vertex. There are 5 weak pairs laterally 

 along the eye margin, 3 strong and longer bristles dor- 

 sally. The proboscis is strongly attenuate from the 

 lateral aspect, terminating in a comparatively narrow, 

 rounded apex ; it is slightly tapered or swollen towards 

 the base from the dorsal aspect; it has a high medial 

 ridge beginning near the base, becoming shorter, and 

 ending near the apex; the latter has only a few, fine, 

 short hairs and the base ventrally has 2 or 3 fine hairs. 

 The proboscis tends to be directed obliquely forward 

 and downward; it is short and rather robust but ex- 

 tends distinctly beyond the face. Palpus minute, dis- 

 tinctly of two segments, the first segment broad, short, 

 convex ventrally, hemicylindrical and excavated and 

 fused medially ; the second segment is a little shorter, 

 quite slender and cylindrical, and bears 1 or 2 excep- 

 tionally fine, slender hairs ventrally at the apex. 



The antenna is attached at the middle of the head ; 

 it is of moderate length and quite slender. The first 

 segment is one-half to two-thirds as long as the second, 

 completely hidden in profile; the second is short, a little 

 widened distally ; the third is not as wide basally as the 

 second segment and including the long, stylelike micro- 

 segment, which is itself as long as the third segment, 



