538 



UNITED STATES NATIONAL MUSEXIM BULLETIN 224 



Pile of abdomen fine, minute, suberect, bristly or setate 

 in character, but the sides of the first three tergites have 

 a little longer pile which is never conspicuous. The first 

 tergite laterally is only slightly protuberant and bears 

 4 slender, lateral bristles and additional, stiff pile. Pos- 

 terolateral margins of the second, third and fourth ter- 

 gites with a row of 4 rather stout, pale, appressed 

 bristles. There are eight tergites in the male, the 

 eighth tergite a third as long as the seventh. Females 

 with seven tergites, with the eighth and the remainder 

 incorporated in the ovipositor. Male terminal ia mod- 

 erately large, elongate, not rotate; the superior dorsal 

 forceps considerably longer than the lateral pair; the 

 last stemite long and undivided. Female terminalia 

 comparatively short, only a little compressed laterally, 

 strongly convex above; the eighth tergite is consider- 

 ably shorter than the seventh. Ninth and tenth tergites 

 moderately long and extended straight backward. The 

 first stemite is apilose, the others with quite short, ap- 

 pressed, bristly pile; the base of the second sternite 

 with some longer, erect, bristly hairs. 



Distribution : Neotropical : Chilesus geminatus Brom- 

 ley (1932). 



Genus Echthistus Loew 



FlQUBES 358, 756, 1507, 1516, 2276, 2323, 2360, 2414 



Echthistus Loew, Linnaea Entomologica, vol. 4, p. 142, 1849. 

 Type of genus : Asilus ruflnervis Meigen, 1820, by original 

 designation. 



Medium size flies or smaller with slender, tapered ab- 

 domen. They are characterized by the long, prominent 

 face, the unusually thick occiput, the vertex which 

 shows little or no excavation. Occipital bristles and 

 pile especially abimdant. The hypopleuron and ptero- 

 pleuron bear bristles. Still more striking is the exag- 

 gerated, tuberculate, spinelike complex of bristles on 

 the ventral surface of the first 4 legs. Length 20 mm. 



Head, lateral aspect: The face is unusually prom- 

 inent, although only moderately produced on the upper 

 fourth beneath the antenna. At this level the face is 

 rather abruptly produced to a moderate extent but the 

 appearance of length is increased by the ventral pos- 

 terior recession of the eye. The eye is also to a moderate 

 extent anteriorly recessive, leaving the eye profile angu- 

 late below; eye imusually long and very strongly con- 

 vex anteriorly ; it is approximately plane through the 

 middle third posteriorly. The occiput is unusually 

 thick, but its thickness is greatest at some distance 

 from the eye margin and extends undiminished nearly 

 or quite to the vertex. Occipital pile scanty through 

 the middle but exceptionally abundant, long and fine 

 behind the vertex and again abundant ventrally ; bris- 

 tles begin below the middle of the head at the lower 

 fourth; number 12 on each side, with an additional 8 

 dorsal bristles which are somewhat more stout; all of 

 them are relatively short and sliglitly curved, and 

 through the middle form a double row. The proboscis 

 is of moderate length, directed obliquely downward, 



comparatively slender, subcylindrical, slightly swollen 

 at the base; the dorsal ridge is high and prominent, 

 the apex gently tapered from below, bluntly rounded 

 and bearing on all sides rather long, stiff pile ; the ven- 

 tral surface as far as the middle has numerous, long, 

 stiff hairs. Palpus of one segment with a distinct trace 

 of the basal segment; the ventral and lateral surfaces 

 bear numerous, long hairs, the apex with many weak 

 bristles. 



The antenna attached to upper third of head, rather 

 slender and elongate, the first segment is not quite twice 

 as long as the second. The third segment is a little 

 longer than the basal two combined; it is nowhere 

 thicker than the swollen apex of the second segment, 

 slightly tapered at its apex, and beare a short micro- 

 segment with a short, thick style carrying an apical 

 spine. The style is two-thirds as long as the third seg- 

 ment. First segment with 6 or more setae above, about 

 10 setae below, several of which are as long as the seg- 

 ment ; second segment with 2 or 3 short setae above and 

 below ; third with 2 or more setae dorsally. 



Head, anterior aspect : The face below the antenna 

 is a fourth of head width, widening below. Subepis- 

 tomal area moderately large, concave and pubescent. 

 The face is microjjubescent, with pile absent except on 

 the lower lateral corners of the epistomal margin. The 

 bristles of the face are numerous; beginning at the 

 upper edge of the gibbosity and extending down the 

 middle half of face they increase in length and stout- 

 ness. Middle of the face with a transverse row of 4 

 especially stout bristles and weak elements immediate- 

 ly below it, followed by a cluster of 10 especially stout, 

 much longer, pale bristles. All bristles slightly curved 

 and directed obliquely forward. Each lateral margin 

 of subepistoma with 6 long, stout bristles. Front 

 slightly divergent, the vertex scarcely convergent. 

 Sides of front with 12 to 14 long, slender bristles or 

 bristly hairs. Vertex scarcely or at most very slightly 

 excavated. Ocellarimn moderately high, bearing some 

 8 pairs of moflerately long, slender, divergent bristles. 

 Eyes scarcely enlarged. 



Thorax: The mesonotum with pleuron pollinose; 

 pile of mesonotum erect, moderately long, fine, some- 

 what curled and setate. There is a wide band of acros- 

 tical setae; dorsolateral bristles are characteristic and 

 become exceedingly stout and long at a level shortly 

 behind the humerus and thence backward with 8 or 9 

 pairs of such bristles. Humerus pilose. Stout, long, 

 lateral bristles are present and consist of 1 posthumeral, 



3 notopleural in transverse row, 3 supraalar, 1 supra- 

 postalar, 3 postalar and 1 pair of scutellar bristles. 

 Scutellar disc thick, convex with imi:)ressed rim, bear- 

 ing a number of fine, erect hairs. Propleuron with 

 abundant, long pile; the pronotum has on each side 

 about 14 exceptionally long, stout bristles. Upper, pos- 

 terior, and anterior mesopleuron and upper sterno- 

 pleuron with some long, stiff pile. Pteropleuron with 



4 or 5 long, slender bristles. Hypopleuron with 3 ex- 

 traordinarily long, very stout bristles. Metapleuron 



