ROBBER FLIES OF THE WORLD 



461 



erately divergent below. The face is pubescent and it 

 may be covered densely over its whole surface with mere 

 coarse pile and no bristles, but more generally there is a 

 triangle of exceptionally stout, long bristles on the lower 

 half of the medial part and also stout bristles are usually 

 continued down tlie sides of the subepistomal area. Tlie 

 ujDper half of the face usually bears a few, scattered 

 hairs, but is sometimes rather densely pilose. The 

 cheeks are prominent. Front short, rather sunken, with 

 an ocular and subocular row of slender bristles and 

 bristly hairs, each row containmg numerous elements. 

 Vertex moderately to deeply excavated, the sides slant- 

 ing to almost vertical. Ocellarium moderately large but 

 rather low. In some species there is pile between the 

 ocelli, in others none ; those which lack pile between the 

 ocelli have a tuft of bristles, hairs, or both on each side 

 behind the ocelli. The eyes are somewhat flattened an- 

 teriorly, with the medial facets enlarged. 



Thorax: The thorax is pollinose, varying from 

 densely to sparsely beset with bristly setae. Acrostical 

 elements may or may not be differentiated. Doreocen- 

 tral elements usually begin at the transverse suture and 

 become long and stout posteriorly ; there may be merely 

 a general lengthening of the dense pile posteriorly. 

 Humerus bristly pilose. The lateral complement of 

 bristles consists of 2 notopleural, 1 supraalar, 1 supra- 

 l^ostalar, 2 or 3 postalar, 3 or 4 pairs of scutellar bris- 

 tles, and sometimes as many more upon the posterior 

 portion of the disc. Tlie scutellum is quite thick, with 

 some evidence of a rim in some species, in others with 

 none. Species like Pai^apromachus leoninus Loew lack 

 notopleural bristles, have only the most slender bristles 

 above the wing or on the postalar and lack tliem upon 

 the scutellum where the whole surface and margin is 

 densely, long, coarse pilose. Similarly, this species is 

 densely pilose on the pleuron and bristles are lacking 

 on the metapleuron, which is also densely pilose. Gen- 

 erally the upper and posterior surfaces of the meso- 

 pleuron are coarsely pilose, or even have bristles. The 

 posterior basalare has several bristles. Postmetacoxal 

 area membranous, the metasternum pilose. Proster- 

 num dissociated. 



Legs: All the femora are stout, but only the first 4 

 are swollen. Bristles are quite stout and comparatively 

 numerous. On the hind femur are 3 to 5 dorsolateral 

 bristles ; the last is located some distance from the apex, 

 but usually quite close to the apex 1 or 2 stout bris- 

 tles dorsomedially. Ventrolateral margin with 2 to 6 

 stout bristles; femora and tibiae with scattered, coarse, 

 subappressed pile, and sometimes a conspicuous fringe 

 of long, coarse hairs ventrally and even longer elements 

 ventromedially ; again, as in Parapromachits leonintts 

 the legs are densely covered with shaggy pile, and re- 

 duced bristles, especially on the tibiae, and their basi- 

 tarsi are greatly shortened. Middle femur with 2 or 3 

 stout bristles along the middle of the anterior and poste- 

 rior surfaces and frequently ventral and ventrolateral 

 bristles as well. Anterior femur with 1 to 2 postero- 

 dorsal bristles near the middle and sometimes an antero- 



ventral bristle. Tlie hind tibia usually has 2 or 3 dorso- 

 lateral bristles, including a stout element at the base 

 and sometimes a few dorsomedial bristles, and from 1 

 or 2 distal ventral bristles; apex with 6 bristles. The 

 anterior and middle tibia have a nearly similar com- 

 plement of bristles. Basitarsus as long as the next two 

 or sometimes the next three segments. Claws sharp, the 

 pulvilli well developed, the empodium bladelike. 



Wings : The wings are long, tending to become a little 

 more slender or pointed apically, with the anal lobe 

 often conspicuously extended, leaving the base of the 

 wing broad. Marginal cell closed with a short stalk. 

 The basal portion of the second subraarginal cell is 

 quite narrow and divided at or usually beyond the pos- 

 terior ci'ossvein by a short, rectangular crossvein, so 

 that the wing has 3 submarginal cells. The second sub- 

 marginal cell is deeply flared and widened distally. The 

 anterior branch of the third vein ends well above the 

 wing apex and the posterior branch ends far behind. 

 Fourth posterior cell closed and stalked ; the anal cell 

 closed; the alula large; the ambient vein complete. 



Abdomen: The abdomen varies fi'om broad and ro- 

 bust basally, narrowed and tapered only on the last 

 three or four segments to species in which it is com- 

 paratively slender basally and gently and gradually 

 tapered throughout its entire length. The wings may 

 reach to the end of the abdomen, but are usually a little 

 shorter. The surface is pollinose, frequently with 

 transverse bands of pale pollen along the posterior 

 margin. Bristles are confined to the first tergite; the 

 pile is coarse, suberect and considerably longer on the 

 first two tergites and laterally on the third or fourth 

 tergites. Sternal pile is coarse and long. Males have 

 eight well developed tergites, the last occasionally being 

 of reduced length dorsally. Females sometimes with 

 only four or five segments which have not been incorpo- 

 rated within the ovipositor; in most species the ovipos- 

 itor may contain as few as three segments. Male 

 terminalia generally with elongate, distally apposed 

 forceps, conspicuous, erect proctiger and a three- 

 pronged aedeagus which may extend far beyond the 

 forceps. The gonopod is generally only half as long 

 as the forceps and the hypandriimi is short. The ovi- 

 positor is only moderately compressed laterally and 

 often quite elongate, or as in other groups, short and 

 only twice as high as wide. 



Distribution : Nearctic : Promachus alhifacies "Willis- 

 ton (1885) ; aldiicMi Hine (1911) ; atrox Bromley 

 (1940) ; JrtsteroJw Macquart (1838) [ = Zaewnw-? Walker 

 {ld,^%),'phi7adelj>hkus^ch.\x\%v (1867), TOS/^zms Walk- 

 er {l?,f>l),%iUinius Walker (1851)] ; dimidmtus Curran 

 (1927) ; fitchii Osten Sacken (1878) ; gigantens Hine 

 (1911) ; Mnei Bromley (1931) ; minusculns Hine 

 (1911) ; nigripes Hine (1911) ; nigropilosus Schaeffer 

 (1916); oklahomemis Pritchard (1935); painten 

 Bromley (1934) ; princeps Williston (1884) ; quadratus 

 Wiedemann (1821) ; rujtpes Fabricius (1775) ; sacheni- 

 Hine (1911) ; texanus Bromley (1934) ; vertehratus Say 

 (1823). 



