ROBBER FLIES OF THE WORLD 



489 



out a microsegment ; the style is thick and longer than 

 the combined length of all three segments, and bears a 

 spine at the apex. 



Head, anterior aspect: The head is wide, with the 

 eyes more or less flattened in front and the medial facets 

 enlarged. The face below the antenna is a fifth the 

 head width and strongly divergent below. The cheeks 

 are unusually high and well developed below the eyes. 

 The face cover is pubescent, generally without pile on 

 the upper half and the gibbous portion bears on its su- 

 perior aspect a few, scattered, moderately long, bristly 

 hairs, which gradually become longer below and later- 

 ally, spreading out to form a triangle, and continued 

 thickly down the lateral margin of the subepistomal 

 area, so that the lower face is fringed or closed with a 

 mystax of dense, quite long, matted, fine, generally pale, 

 bristly hairs. The front is divergent and again con- 

 vergent near the vertex. It is comparatively large, 

 sunken medially, with a wide lateral band of dense, 

 bristly pile. Vertex moderately excavated with nearly 

 vertical sides that bear pile and with a wide, rather 

 high, rounded ocellarium. There is a row of bristly 

 pile along the medial border of each posterior ocellus 

 continued posteriorly behind the ocellus. 



Thorax : The mesonotum is relatively low, long, and 

 pollinose, with greatly reduced pile. The pile consists 

 of scattered, nearly erect setae, longer above the wing, 

 and bristles are only differentiated shortly before the 

 Anteriorly are 4 poorly defined rows of acrostical setae 

 separated into groiips of 2 each and doreocentral pile 

 and bristles are only differentiated shortly before the 

 scutellum, where there are generally 2 or 3 pairs of long, 

 stout bristles. The lateral complement of long, stout 

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

 postalar, 2 postalar, and no scutellar bristles on the rim 

 proper. The very thick, convex scutellum does show on 

 each side ; distributed through the middle portion there 

 is a cluster of 5 to 8 long, stout bristles and the whole of 

 the faintly pollinose surface is densely beset with long, 

 erect, coarse or bristly hairs ; there is a faint trace of the 

 impressed rim. Pronotum with 10 to 15 pairs of stout 

 bristles and other pile. The whole dorsal border of the 

 mesopleuron, its posterior half, most of the anterior 

 basalare, the upper half of the sternopleuron, middle 

 half of the pteropleuron, the posthypopleuron, all bear 

 abundant, long, bristly pile. Metapleuron with similar 

 pile and a vertical row of 6 to 8 quite stout bristles. 

 Metanotal callosity pollinose only. Metasternum long 

 pilose laterally and below. Postmetacoxal area with a 

 rather wide arch of chitin joined anteriorly and notched 

 behind. Prosternum dissociated. 



Legs : The femora are stout and comparatively long 

 and only the first 4 femora slightly thickened. The 

 pile of femora and tibiae is unusually abundant and 

 everywhere coarse and bristly; it is especially bristly 

 on the dorsal surfaces of the first 4 tibiae and their 

 femora; it is conspicuous and longer on the ventral 

 surface of the hind femur. The hind tibia dorsally, 

 ventrally and laterally has a conspicuous, dense fringe 



535914— 62— pt. 2 5 



of rather long, pale pile. Bristles are stout, numerous 

 and rather blunt. The hind femur has 3 or 4 dor- 

 solateral bristles distributed along the middle, 6 ven- 

 trolateral bristles, 2 dorsomedial bristles at the sub- 

 apex. The hind tibia has 3 prominent, dorsolateral 

 bristles, one of them at the base and 2 similar, ven- 

 trolateral bristles on the outer half; the apex bears 6 

 bristles. The middle femur shows 6 prominent, pos- 

 terodorsal bristles, 4 anteroventral, 3 ventral and 6 to 

 8 posteroventral bristles. Middle tibia with 2 postero- 

 dorsal, 5 anterodorsal, 2 distal anteroventral, and 4 or 



5 posteroventral bristles. The anterior femur shows 

 only 5 spikelike, ventral bristles, restricted to the basal 

 half; its tibia has a single, basal, anterodorsal bristle, 



6 posterodorsal bristles and 2 or 3 posteroventral 

 bristles ; its apex bears at least 10 bristles. Claws sharp ; 

 pulvilli and empodium long. 



Wings : The wings are long, broad basally with the 

 anal lobe moderately extended distally; the marginal 

 cell is closed with a rather long stalk. Both branches 

 of the third vein end distinctly above the wing apex 

 and the former arises abruptly from the latter, and at 

 nearly right angles. Fourth posterior cell closed with 

 a long stalk. Alula large, the ambient vein complete. 



Abdomen: The abdomen is broad and robust, espe- 

 cially on the first four segments. The first tergite beai-s 

 a few, stout bristles concealed by a dense, bushy tuft 

 of long, coarse, concolorous pile. There are similar 

 tufts of conspicuous pile in the posterior comer of the 

 second segment and the lateral fourth of the third seg- 

 ment. The pile is normally erect but the posterior por- 

 tion of it tends to become matted and subappressed. 

 Sternites with long tufts of pile of a more scattered 

 character. The middle portion of the second to fourth 

 tergites and almost the whole of the succeeding tergites 

 are nearly bare, pile being fine, quite short and scanty. 

 Males with eight tergites but the eighth is almost com- 

 pletely concealed dorsally and appears as a small lip 

 laterally. Male terminalia conspicuous and large but 

 short. The superior forceps broad at the base, bluntly 

 roimded apically ; the gonopod is wide but shorter tlian 

 the forceps, the eig'hth sternite is prominent and the 

 hypandrimn absent or concealed. The aedeagus forms 

 a long, two-pronged, extensive process, extending far 

 beyond the apex of the hypopygium. 



Distribution: Nearctic: Eccritosia ampMnome 

 Walker (1849) [=Uricolor Walker (1850)]; zamon 

 Townsend (1895). 



Neotropical: Eccritosia larlata Fabricius (1787); 

 harhielUnii Curran (1934) ; plinthopyga Wiedeman 

 (1821). 



Genus Satanas Jacobson 



FiGUBES 389, 704, 1422, 1431, 2335, 2345, 2470, 2471 



Satanas Jacobson, Ann. Mus. Zool. Acad. Imp. Sci. St. P^ters- 

 bourg, vol. 13, p. xxxvi, 1908. Type of genus : Proctacanthus 

 gigas Eversmann, 1855, by original designation. 



Very large, conspicuous flies with an elongate abdo- 

 men which is strongly tapered especially in the female. 



