DASTPOGONIXAH 



ROBBER FLIES OF THE WORLD 



125 



The type of genus Stenopogon sabaudus, a southern 

 European species, has the first posterior cell widely 

 open. Of 10 large Asiatic species of Stenopogon ex- 

 amined by me, 9 have the first posterior cell closed and 

 stalked ; 1 species has this cell half closed. Scleropogon 

 as defined by the type of genus appears to be a New 

 World form confined to the western American coast, 

 the Sonoran region and Central America. Stenopo- 

 gon, excepting 1 or 2 species is found in the Palae- 

 arctic region, especially southern Europe and in the 

 Oriental region, especially southern Asia and also 

 widely over southern and western North America but 

 concentrated only in the west. Kertesz listed 13 species 

 under Scleropogon from the Palaearctic; many of these 

 appear to belong to Stenopogon, perhaps all of them. 

 The antenna in Scleropogon varies from short to long. 

 Length of flies 17 to 35 mm. 



Head, lateral aspect: The face is prominent, some- 

 times unusually protuberant and generally with a small, 

 abrupt or gently sloping ridge a short distance below 

 the antenna. This upper portion of the face is nearly 

 plane with the eye. Eye of moderate length, strongly 

 convex, distinctly more narrow below due to a strong, 

 gradual recession of the eye. Occiput characteristically 

 swollen but cliiefly swollen medially, so that it slopes 

 down gently to the eye margin. Pile of occiput dense 

 and bristly and rather long ventrally and replaced by 

 long, coarse pile behind the cheeks, where there is a 

 dense, rather protuberant ledge, which may extend back 

 from the proboscis. Upper occipital pile almost wholly 

 composed of a wide band of bristles extending deep 

 within the medial portion, the more anterodorsal ele- 

 ments stouter. Proboscis long, rather slender, nearly 

 subcylindrical, medial dorsal ridge present or absent; 

 proboscis not swollen toward the base, the apex only 

 slightly narrowed; the apex bears a few, stiff hairs; 

 the base below has some long pile. The proboscis is 

 directed obliquely downward. Palpus with the first 

 segment excavated, the second porate with numerous, 

 ventral, dorsal, medial and lateral bristles. 



Head, anterior aspect : The face below the antenna is 

 one-sixth of head width and strongly divergent below. 

 Subepistomal area relatively small, and nearly horizon- 

 tal, concave and bare. Face micropubescent with nu- 

 merous exceptionally stout, long bristles extending over 

 the lower three- fourths or more of the face and absent 

 only from the nearly plane portion beneath the antenna, 

 these bristles may extend beyond the proboscis and are 

 curved obliquely downward and there may be a few, 

 short, stiff hairs among them. Antenna attached at or 

 a little above the upper third of the head, elongate and 

 slender, the first segment a little longer than the sec- 

 ond. The third segment is V/ 2 to 2 times as long 

 as the first two combined; it is slightly attenuate and 

 at the apex has two microsegments, the first rather 

 short, the second five or six times as long as the first 

 microsegment, attenuate apically and carrying a dis- 

 tinct, apical spine. These microsegments are usually 

 held at a slight angle laterally. First segment with 



numerous, stout bristles ventrally, several of which may 

 be as long as the first two segments combined and with 

 shorter ones dorsally. Second segment with 2 or 3 

 short, stout bristles dorsally and ventrally. Front nor- 

 row, slightly wider than the upper face and slightly 

 convergent at the vertex or sometimes of equal width. 

 Characteristically the front has a subocular row of 8 

 to 12 or more stout bristles; surface pollinose. Vertex 

 very little excavated, the ocellarium large, low and bear- 

 ing in the middle 1 to 4 pairs of long, stout bristles and 

 sometimes as many more postocellar bristles. Eye 

 facets only a little enlarged. 



Thorax : The thorax is pollinose. The mesonotal pile 

 consists of numerous, rather short, subappressed setae 

 which become a little longer posteriorly and behind the 

 humerus. Acrostical elements are undifferentiated but 

 stout dorsocentral bristles may begin behind the hu- 

 merus. The mesonotal bristles are long and stout. The 

 humeral bristles number 6 to 13. There is a group of 



5 to 8 posthumeral bristles. Notopleural bristles consist 

 of 4 to 6 in a transverse row, supraalar with 8 in a 

 longitudinal row or as many as 16 in a single cluster. 

 There may be S to 10 postalar bristles and a wide, trans- 

 verse band of prescutellar elements, besides 4 or 5 pairs 

 of scutellar bristles. All these lateral bristles are ex- 

 ceptionally long and stout. Scutellum convex, pol- 

 linose, apilose, fused to the base. Propleuron with 

 abundant, long, fine pile below; similar pile of weak 

 bristles on the coxa. Anterior pronotum with a double 

 row and postpronotum with a very large cluster of 

 numerous bristles. Mesopleuron characteristically 

 without pile or bristles. A conspicuous tuft of rather 

 long, fine hairs is present on the anterior and postero- 

 dorsal sternopleuron. Pteropleuron and hypopleuron 

 apilose. Metapleuron always with pile or bristles or 

 both; metanotal slopes pubescent only; lateral meta- 

 sternum apilose, the ventral metasternum with abund- 

 ant, long pile, the first tergite always with some pile. 

 Postmetacoxal area membranous. 



Legs: The legs are stout without being swollen, 

 carrying an unusually abundant complement of stout, 

 moderately long bristles; the pile is dense, fine, and ap- 

 pressed. The hind femur has the following bristles; 



6 to 10 lateral, 8 to 18 ventral, and at the apex laterally 

 an oblique row of 3 to 6 and similar medial row of 6 or 

 7; sometimes also 2 or 3 bristles medially and sub- 

 apically. The hind tibia shows 1 to 4 medial, 5 dorso- 

 medial, 4 to 7 dorsolateral, 5 to 9 ventrolateral, the 

 subapex has 9 bristles. Middle femur with 3 to 5 stout, 

 anterior, distributed along the middle, and an oblique 

 apical row anteriorly of 3 or 4; also 1 to 3 posterior, 

 subapical and a double or triple ventral row of 6 or 7 

 pairs of bristles. The middle tibia has 6 anterodorsal, 6 

 posterodorsal, 5 or 6 posterior, 4 ventral and 2 anter- 

 oventral bristles. The anterior femur has 1 to 3 an- 

 terior bristles in the middle, 2 or 3 posterior in the 

 middle or sometimes none, 8 or 9 ventral bristles and 

 then maybe as many as 18 dorsal bristles or none. An- 

 terior tibia with a double dorsal row of 6 to 8 pairs, 

 also 8 stout, long, posterior bristles. Apex of this tibia 



