LAPHRHNAC 



ROBBER FLIES OF THE WORLD 



399 



long, well developed, erect, pale, ventral bristle and 3 or 

 4 additional, short setae above and below. Second seg- 

 ment with a circlet of short bristles, except medially. 



Head, anterior aspect : The face below antenna is a 

 fourth the head width and is slightly reduced in width 

 below. Subepistomal area small, oblique and bare. The 

 face is micropubescent and bears 10 to 12 short, curled 

 hairs on either side. Along the epistomal margin is a 

 widely spaced row of 4 pairs of very slender, long, 

 bristly hairs, and above these a single pair of widely 

 spaced hairs. The front is quite short, pubescent, with 

 3 or 4 fine hairs laterally and no bristles. The vertex 

 is deeply excavated and considerably wider than the 

 face and with slanting sides. Ocellarium prominent 

 and quite high, the steep sides bearing a single pair 

 of strong, divergent bristles. Anterior central eye 

 facets very strongly enlarged. 



Thorax : The mesonotum is punctate, without pollen 

 or pubescence ; the pleuron bears a middle and an an- 

 terior stripe of micropubescence meeting above ; meta- 

 pleuron and the hypopleuron also pubescent. The 

 pile of the mesonotum is abundant, short, flat appressed 

 and rather curled and setate but without differentiation. 

 The lateral margin has 1 notopleural, 1 supraalar, 1 

 postalar, but no scutellar bristles. Scutellum convex, 

 punctate, with pile similar to the niesonotum. Meso- 

 pleuron with fine pile dorsally and ventrally and a 

 single, slender bristle. Metapleuron with a band of 

 long, straight or slightly curved, bristly hairs. Hypo- 

 pleuron with some pile. Pteropleuron polished and 

 apilose. The lateral metanotal slopes bear 1 stout, stiff 

 bristle and a few, short hairs. Lateral metasternum 

 with pile ; ventral metasternum with a few long hairs ; 

 postmetacoxal area chitinized but rather short; tegula 

 pubescent only. Prosternum not dissociated. 



Legs : The hind femur is a little thickened especially 

 through the middle ; it bears the following complement 

 of bristles : 1 long, stout, pale, erect, lateral bristle at the 

 outer third, but no apical bristles. This tibia has 3 

 rather long, lateral bristles. The hind femur ventrally 

 bears only a few, quite scattered, long, erect hairs but 

 has 3 very long, erect, slender, ventromedial bristles at 

 the middle and base; the hind tibia ventrally has a 

 rather copius, erect fringe of long pile and no setae. 

 Middle tibia with 3 long, basally stout, anterior and 

 posterior bristles. Anterior tibia with similar bristles 

 but with the anterior element quite short. The bristles 

 of the anterior basitarsi and following segment are 

 long on both sides. Tarsi end in slender, sharp claws, 

 well developed pulvilli, and a short empodium. 



Wings: The wings are unusually broad. The mar- 

 ginal cell is closed and stalked ; the anterior branch of 

 the third vein ends just above wing apex; the posterior 

 branch far behind. The first posterior cell is narrowly 

 open, the fourth is closed and stalked. The third pos- 

 terior cell is united with the second posterior cell so 

 that only 4 posterior cells are present. The vein end- 

 ing the fourth posterior cell and the single vein ending 

 the discal cell are in almost a straight line; anal cell 



closed and stalked, evanescent marginally. Alula of 

 medium width; the ambient vein ends with the first 

 posterior cell. 



Abdomen : The abdomen is comparatively broad and 

 robust, as wide as the thorax and strongly, coais.lv 

 punctulate. Pile short, fine and scanty. Sides of the 

 first tergite with 4 stout, pale bristles; the middle of 

 the sublateral margin of each remaining lergite with 1 

 quite stout bristle. There are six termites present in 

 the male and six in the female with the seventh con- 

 cealed as a short flap beneath the sixth. Male termi- 

 nalia rotate and of the general form of Atomosia. The 

 terminalia are small, subglobular like in Atomosia and 

 recessed and hidden within the cavity formed by the 

 obtuse, convex, ultimate tergites. Beyond the epan- 

 drium is a long, polished, arched proctiger, extended 

 beneath the encircling attenuate gonopod arms, which 

 are larger and dominate the structure; aedeagus is a 

 flat tube divided apically into 3 quite short branches. 

 Female terminalia quite short and concealed or in pro- 

 file extending only a short way beyond the edge of the 

 tergite; the eighth sternite is produced a short distance 

 without lobes or processes. 



Distribution: Nearctic: Atomosiella antennata 

 Banks (1920). 



Genus Rhathimomyia Lynch Arribalzaga 

 Figures 230, 652, 1316, 1325 



Rliathimomyia Lynch Arribalzaga, Anal. Soc. Cient. Argentina, 

 vol. 14, p. 135, 1882. Type of genus: Rhathimomyia nitidula 

 Lynch Arribalzaga, 1882, by original designation. 



Rliathilhnmyia Williston, Trans. American Ent. Soc, vol. 18, 

 p. 7S, 1891, lapsus. 



Small flies, black with polished, shining, micropune- 

 tate, rather broadly oval abdomen, which tends to be 

 a little flattened along the middle. Scutellum flattened 

 on the disc and without spines or bristles. The hind 

 femur is stout, a little swollen distally, and bears a 

 partly doubled row of weak spines or spinous bristles 

 which arise from weak tubercles. Length 9 mm. 



Head, lateral aspect: The face is quite short and 

 nearly plane with a very slight depression over the 

 middle face ; therefore, there is almost no gibbous por- 

 tion ventrally. Subepistoma small and nearly hori- 

 zontal. Occiput moderately well developed except the 

 part back from the eye margin. At the lower corners 

 of the occiput are only a few bristly hairs or quite weak 

 bristles. Below, the middle bristles become rather 

 strong; they are situated in a single row and dorsally 

 are almost spikelike; there are 14 on each side. Pro- 

 boscis small, short, subcylindrical, slightly compressed 

 and linearly striate laterally, with the apex truncate 

 and a little expanded. It is directed straight forward. 

 Narrowly about the apex of the proboscis is a circlet of 

 fine hairs; base below with a few hairs and in lateral 

 view the base is strongly depressed and without keel, 

 in contrast to Atomosia Macquart. Palpus extraordi- 

 narily minute, slender and cylindrical, with a few fine 



