ROBBER FLIES OF THE WORLD 



563 



stiff hairs below and laterally. The whole structure is 

 cylindrical, extending beyond the face. Palpus of one 

 segment, elongate, with numerous bristles and with a 

 trace of the basal segment. The antenna are attached a 

 little above the middle of the head ; they are compara- 

 tively elongate and together with the style are fully as 

 long as the head. The fii-st and second segments are 

 long, the second segment only a little shorter than the 

 first ; the first segment bears 2 or 3 pairs of long, stout 

 bristles ventrally and other long, stiff hairs both ven- 

 trally, laterally, and above. The third segment is elon- 

 gate and nearly as long as the first two combined but 

 usually not wider than the second segment; it bears a 

 short microsegment followed by a moderately long, 

 stout style, with apical bristle. Style and microsegment 

 together are as long as the third segment. 



Head, anterior aspect : The face below the antenna is 

 a fifth the head width and strongly divergent below; 

 it is pubescent, generally with little or no pile but with 

 the middle third and gibbous portion bearing numerous, 

 long, slender or stout, curved bristles. Subepistomal 

 area large, oblique, concave, bordered by numerous, 

 slender bristles. The cheeks are moderately large and 

 also pubescent. Front short, pubescent with an ocular 

 row of short bristles on the upper front and continued 

 back between the ocelli, and with a similar, linear, 

 subocular row confined to the front. The front is a 

 little widened, more strongly narrowed at the vertex. 

 The vertex is deeply excavated, the ocellariimi large, 

 with 3 or 4 pairs of bristles between the ocelli and 2 or 

 3 pairs of postocellar bristles. Upper occipital bristles 

 especially stout and barely curved or straight. 



Thorax : The mesonotum is high and rather abrupt 

 both anteriorly and posteriorly; it is pollinose with 

 rather dense, nearly erect, comparatively long setae. 

 Acrostical elements are not differentiated and dorso- 

 central bristles occur only posteriorly where there may 

 be 4 to 9 in each row, long and stout. Humerus with 

 setae and pile. The lateral complement of long, stout 

 bristles consists of : 1 weak posthumeral, 2 notopleural, 

 1 supraalar, 1 postsupraalar, 2 postalar, and 2 to 5 pairs 

 of scutellar bristles. Scutellum convex, thick, with dis- 

 tinct impressed rim, pollinose and with rather dense, 

 long, bristly pile on the disc and sometimes in the mar- 

 gin. ]\fetanotal callosity with a dense tuft of bristly 

 pile. Pronotum with stout bristles and dense pile. 

 Upper and posterior mesopleuron with pile and a few 

 setae ; stemopleuron with scattered hairs ; pteropleuron 

 with a tuft of long pile ; anterior basalare with 2 or 3 

 small bristles; posthypopleuron and metapleuron with 

 a vertical row of both long, stout bristles and bristly 

 pile. Prostemum dissociated. Postmetacoxal area 

 membranous. 



Legs : The femora are quite stout, the first 4 a little 

 thickened. The pile of the legs consists of dense, ap- 

 pressed bristles or setae ; the bristles are stout, a little 

 blunt at apex and numerous, especially on the last 4 

 femora. Hind femur with 5 dorsolateral bristles, a 

 medial pair of bristles set some distance from the apex, 

 a vertical row of 3 lateral and an oblique row of 3 



medial bristles close to the apex, 8 ventrolateral, and 6 

 ventromedial bristles. Middle femur with 2 anterior 

 bristles, and 2 anteroventral, or sometimes as many as 

 4. Posteriorly, there is an oblique row of 3 bristles 

 at the apex, 1 anteriorly at the apex, and 1 ventrally, 

 sometimes absent. Anterior femur usually with 1 or 



2 bristles at the apex anteriorly, sometimes ventrally 

 and in the type of genus two posterodorsally beyond 

 the middle. All these femora have rather dense, long, 

 stifi" pile ventrally and laterally. Hind tibia with only 



3 bristles dorsolaterally, 2 dorsomedially and 2 ventro- 

 laterally; sometimes with 1 ventromedially. Remain- 

 ing tibia with similarly reduced bristles. The anterior 

 tibia may have only a single, long, stout bristle posteri- 

 orly, 7 short, posterodorsal bristles, 2 stout, basal anter- 

 obasal bristles ; also it has an apical circlet of 8 bristles. 

 Claws sharp, strongly bent at the apex; the pulvilli 

 and empodium large. 



Wings : The marginal cell widened in both sexes at 

 the expense of the subcostal cell, especially so in the 

 male and also moderately rippled. The marginal cell 

 is closed and petiolate ; both the first and second poste- 

 rior cells are wide at the margin ; the base of the second 

 posterior cell is widened, twice as wide at the end of 

 the discal cell. Fourth posterior cell closed and stalked ; 

 anal cell closed, alula large, the ambient vein complete. 



Abdomen: The abdomen is comparatively robust at 

 the base, cylindrical and slightly tapered; the pile is 

 flat appressed and setate ; the sternites bear long, bristly 

 pile and weak bristles. Sides of first tergite with 5 or 



6 long, stout bristles. The subapical posterior margin 

 of at least the second to fifth tergites bear very promi- 

 nent, stout bristles on fvilly the outer third; each seg- 

 ment usually has about 3 or sometimes as many as 



7 bristles. Male with eight tergites but the eighth 

 greatly shortened medially and longer laterally. Fe- 

 male with seven tergites excluding the ovipositor. Male 

 terminalia large; the superior forceps prominent, 

 divergent, but the apices converging and apposed ; the 

 dorsal proctiger is small, oblique, and erect. The gono- 

 pod is considerably shorter, the hypandrium extremely 

 short. The eighth stemite characteristically is pro- 

 duced in most species into a rounded bristle-beset, 

 scooplike process or lappet. The female ovipositor is 

 composed of the moderately long, strongly compressed 

 eighth segment together with the short ninth and the 

 comparatively long, free, dorsal proctiger. 



Distribution: Nearctic: Machimus avidus Wulp 

 (1869) ; occidentalis Hine (1909). 



Neotropical: Machimus tenebrosus Williston (1901) 

 [=^meMS Hine (1906)]. 



Palaearctic: Machimus aterrans Schiner (1868) 

 [ = oophorus Loew (1871)] ; acanthodes Loew (1849) ; 

 alter Becker (1923); annulipes Brulle (1832) i^las- 

 alls Loew (1849), cerdo Gerstaecker (1861)]; anten- 

 natus Becker (1908) ; armipes Becker (1913) ; atricapil- 

 lus Fallen (1814) [ = bicornis Zeller (1840), opams 

 Meigen (1820), Iplebeius Meigen (1820), rufimanus 

 Meigen (1820), subulatus Loew (1840)], atricapiUus 



