ROBBER FLIES OF THE WORLD 



507 



level of the humerus. They become long on the pos- 

 terior third of the mesonotum. Humerus with bristly 

 pile. There are 1 or 2 posthumeral bristles and the 

 lateral complement of long, stout bristles contains 2 

 notopleural, 1 postsupraalar, 1 to 3 suprapostalar, 2 

 postalar, and 1 pair of strong scutellar bristles, with 

 some additional bristly hairs. The scutellum is only a 

 little thickened, convex, with distinct impressed rim. 

 Pronotiun with 2 or 3 pairs of weak bristles and some 

 fine pile. Upper margin of the mesopleuron with a 

 band of 15 or more distinct, though slender bristles, all 

 quite long. Anterior basalare below with a row of 6 or 

 7 stiff hairs, along the rim. Posterior margin of the 

 mesopleuron without pile, but the upper sternopleuron 

 and upper pteropleuron witli a conspicuous tuft of 

 long, coarse hairs and the pteropleuron with 2 slender 

 bristles. Posthypopleuron with some pile, the meta- 

 pleuron with a narrow band of 10 or 11 slender bristles. 

 Metanotal callosity poUinose only. Metasternuin 

 pilose; postmetacoxal area membranous. Prosternum 

 dissociated. Anterior basalare with bristly hairs on the 

 anteroventral margin. 



Legs : All the femora are stout but only the anterior 

 four swollen. The hind femur and to a less extent its 

 tibia are lengthened and more elongate. The pile is 

 coarse, rather long and flat appressed. Only the 

 femora have ventral fringes of long, stiff or bristly 

 hairs and they grow more conspicuous from the liind 

 pair to the front pair. Bristles are rather numerous, 

 stout and sharp. The hind femur bears 4 lateral, 15 

 ventrolateral in a partly double row, and 7 or 8 very 

 slender, pale ventromedial bristles, besides a spikelike, 

 black bristle ventromedially near the apex. Also, dor- 

 sally at the subapex is a bristle on each side, but at the 

 apex only stiff, bristly hairs a little longer than the 

 setae. The hind tibia bears just beyond the middle, 2 

 dorsolateral, 1 dorsomedial, and 2 ventrolateral 

 bristles; apex with 8 bristles. Middle femur with 3 

 stout bristles anteriorly, 7 others anteroventrally ; its 

 tibia has 1 long, stout and 1 slender, anterodorsal 

 bristle, 6 posterodorsal bristles, only 2 of them stout, 3 

 posterior bristles, 1 posteroventral and 2 anteroventral 

 bristles, all stout and confined to the outer half. An- 

 terior femur without prominent bristles but with some 

 bristly hairs and much long, coarse hairs ventrally. 

 The anterior tibia has 1 rather stout bristle near the 

 base dorsally, 8 moderately long posteroventral bristles. 

 Anterior and posterior bristles of the tarsi long, stout 

 and oblique. Claws slender, sharp, bent at the apex; 

 the pulvilli and empodium well developed. 



Wings: The wings are tinged with brown on the 

 apical third. The marginal cell is comparatively wide, 

 including the apex and closed with a moderate stalk. 

 The anterior branch of the third vein ends barely be- 

 fore the wing apex, the posterior branch some distance 

 behind. The base of second posterior cell only mod- 

 erately and gently widened. Anterior margin of fourth 

 posterior cell rather strongly convex, partly occluding 

 the discal cell. Fourth posterior cell closed with a 



short stalk, the anal cell likewise. Alula large, the am- 

 bient vein complete. 



Abdomen: The abdomen is comparatively slender, 

 cylindrical and slightly tapered. The pile is scanty, 

 fine, setate and appressed with a little long, fine, erect 

 hair on the sides of the first three segments. There are 

 2 pairs of stout bristles laterally and a posterior, middle 

 fringe of bristly hairs on the first tergite. Males with 

 eight tergites, the eighth is a third to half as long as 

 the seventh ; seventh tergite with 7 or 8 slender bristles 

 along the posterior margin, and the eighth sternite with 

 a dense, conspicuous band of slender, black bristles 

 thrust obliquely downward. Male terminalia elongate, 

 not rotate. The superior forceps broad and flat apically 

 and laterally compressed, closely apposed posteriorly, 

 with the short proctiger extended obliquely upward. 

 The gonopod is short but the hypandrium is large, with 

 a cuplike excision ventrally and medially and laterally 

 extending more than half way up the sides of the ter- 

 minalia. In general these terminalia suggest PhUonicus 

 Loew in appearance but there is no posterior dorsal 

 opening. The female terminalia consist of the eighth 

 to tenth segments. In the only female before me there 

 is a marked lateral compression but some of it may be 

 unnatural and apparently the normal shape is not quite 

 cylindrical. The eighth segment is about twice as long 

 as high. The ninth tergite is extremely short and but- 

 ton-like, and the tenth is smaller, cylindrical, twice as 

 long as wide, with obliquely concave apex, and with the 

 apex below. The tenth ventral element is a flattened 

 and greatly compressed structure with broadly and 

 evenly rounded, apposed, apical plates. 



Distribution: Nearctic: Regasilus hlantoni Bromley 

 (1951). 



Neotropical: Regasilus strigaria Curran (1931). 



Genus Eraxasilus Carrera 



Eraxasilus Carrera, Opuscula Zoologica, no. 30, p. 6, 1959. 

 Type of genus : Eraxasilus pruinosus Carrera, 1959, by orig- 

 inal designation. 



The following description is from Carrera. 



Characters — Face slightly wider on the buccal margin ; facial 

 callosity large, occupying two thirds the length of the face and 

 with bristles on all its surface ; proboscis cylindrical, not swollen 

 at the base ; third antennal segment fusiform ; arista little 

 larger than this same segment and with a small apical swelling. 

 Mesonotum without median longitudinal crest; lateral and 

 posterior dorsocentral bristles developed, anterior dorsocentrals 

 small ; acrostical bristles short, larger posteriorly ; pteropleura 

 with very scanty pilosity ; scutellum with marginal bristles ; cal- 

 losities of the postscutellar region without hairs. Hind femora 

 not very thick, with short bristles, without any differentiated 

 structure. Wings with two submarginal cells ; bifurcation of 

 the "da." longitudinal vein in an angled curve and without any 

 vestige of vein appendage at its base; the posterior branch of 

 bifurcation of the third longitudinal vein is more or less straight 

 and ends a little before the apex of the wing. Abdomen going 

 a little beyond the apex of the wings when these are extended 

 over it ; posterior margin of the segments without differentiated 

 bristles ; genitalia of the $ distended in the same direction as 

 the abdomen, without forming an angle with it ; ninth sternite 

 large, rounded ; ovipositor short, laterally compressed. 



