248 



UNITED STATES NATIONAL MUSEUM BULLETIN 224 



PART 1 



Genus Rachiopogon Ricardo 



Figubes 96, 551, 1088, 1097, 1613, 1838 



Rachiopogon Ricardo, Ann. Nat. Hist., ser. 8, vol. 9, p. 590, 1912. 

 Type of genus : Dasypogon grantii Newman, 1857, by 

 original designation. 



Large flies of bare appearance with extremely short 

 pile. The hind femur and tibia are elongate and slen- 

 der, the former a little thickened distally; all of the 

 posterior cells are widely open. Face moderately pro- 

 duced, with bristles restricted to the epistomal margin 

 and pile absent on the whole of the face. Readily 

 distinguished from allied genera by the absence of the 

 anterior intercalary vein, the conical, stylate microseg- 

 ment on the third antennal segment, and the char- 

 acteristic male terminalia reminiscent of Chrysopogon 

 Roeder. The hypandrium is sulcate, greatly shortened 

 in the middle, the superior elements all quite elongate, 

 including the simple, subcylindroid epandrium and 

 long, similar proctiger. Length 20 mm. 



Head, lateral aspect: The face is moderately pro- 

 duced throughout, never becoming very prominent but 

 slightly more produced on the lower third so as to 

 leave the intervening space concave. The eye is of 

 moderate length but unusually high, rather flattened 

 and only slightly convex along the middle portion. 

 Posteriorly, it is nearly plane in the middle but 

 strongly, convexly recessive above and below. Occiput 

 is short throughout its entire length, the eye rising 

 above the occiput dorsally and extending beyond it 

 laterally. Pile of occiput only moderately abundant 

 and long, but coarse; delicate bristles appear in the 

 middle or even below the middle and often consist of 

 20 on each side ; the more dorsal elements a little more 

 stout. Proboscis is slender, slightly tapered laterally 

 to a rounded point, a little more swollen towards the 

 base dorsally and it is a little longer than the face or 

 extends a little beyond the face. Palpus prominent, 

 clearly of two segments; the first segment is a little 

 more than half as long as the second, distinctly ex- 

 cavated, free medially as well as laterally; the second 

 segment is clavate and bears numerous, dorsal, bristly 

 hairs that extend from the base laterally and extend 

 ventrally from the outer half ; there is some additional, 

 somewhat more stiff, apical pile and 5 and 6 slender 

 bristles. There is a distinct, rather large apical and 

 lateral pore. First segment with numerous bristly hairs 

 ventrally and at its apex; the second segment arises 

 from the side. 



The antenna is attached at the upper fourth of the 

 head; the first 2 segments are short and stout, the 

 first being slightly longer than the second; third seg- 

 ment missing, described by Ricardo as being, "cylin- 

 drical, the notch at the apex best seen from behind and 

 armed with a very short, blunt spine." First segment 

 ventrally and ventrolaterally at the base with 5 short, 

 bristles, a black seta laterally in the middle and 3 or 4 

 short setae dorsally; second segment with 3 ventro- 

 lateral, basal, short setae, and 8 longer dorsal bristly 

 setae. 



Head, anterior aspect: The face below the antenna 

 is two-fifths of the head width and slightly divergent 

 below. Subepistomal area rather large, oblique, deeply 

 concave and bare. Face densely and minutely pubes- 

 cent or pollinose, apilose with 5 pairs of rather long, 

 stout, pale bristles transversely across the epistoma; 

 subepistomal margins without bristles. Front rather 

 large and long, pale pollinose, with a single slender 

 bristle near the middle of each half and set a short 

 distance in front of the ocelli. Side margins and the 

 remainder of the front quite without bristles or pile. 

 Vertex moderately excavated with steeply sloping sides, 

 the ocellarium large, rather high and domelike, with 

 slanted sides, large ocelli, and a pair of stout, rather 

 long, curved, divergent bristles directed forward and 

 arising behind the ocelli. Anterior eye facets strongly 

 enlarged and zoned. 



Thorax : The thorax is thinly pollinose, dark in ap- 

 pearance but light reddish brown in oblique lights. 

 The mesonotum is abrupt anteriorly, gently sloping 

 behind. Pile of mesonotum is scanty, short, bristly 

 and appressed. There is a distinct row of minute, 

 appressed, acrostical pile widely separated from simi- 

 lar dorsocentral pile. The latter is poorly differenti- 

 ated laterally on the anterior half, but developed be- 

 hind the suture into 3 or 4 pairs of moderately long, 

 stout bristles. Humerus with short, bristly hairs only. 

 The lateral bristles are long and stout and consist of 2 

 notopleural, set rather far apart, 2 supraalar, 2 postalar, 

 and an equally stout pair of long scutellar bristles. 

 Scutellum flat, the margin, however, a little rounded ; 

 the base with a shallow crease and no pile. Propleuron 

 ventrally with a dense, large tuft, of fine, stiff pile, the 

 pronotum with 7 pairs of slender bristles, the postero- 

 lateral pronotum with some scattered, fine hair and a 

 single, distinct, rather long, stout bristle. Mesopleuron 

 apilose, sternopleuron with 1 or 2 minute hairs dorsally, 

 pteropleuron and hypopleuron apilose, the convex meta- 

 pleuron especially convex and creased behind, with a 

 vertical row of 5 long, slender bristles and some, addi- 

 tional, bristly hairs. Lateral metanotum pollinose only 

 and protuberant. Posterior half of the lateral meta- 

 sternum with a few, fine hairs, the chitinized ventral 

 matasternum apilose ; postmetacoxal area membranous, 

 tegula with several setae; the anterior basalare with a 

 row of 7 or 8 short, bristly hairs. 



Legs: The legs are comparatively slender, the hind 

 femur very slightly widened apically. All the femora 

 dorsally, the hind pair laterally, the other pairs an- 

 teriorly with moderately abundant, quite fine, short, 

 appressed pile; posterior surfaces of all femora, es- 

 pecially ventrally, almost without pile. Ventral sur- 

 face of the hind tibia with scanty, appressed pile, except 

 on the outer third where there is a brush of ranked 

 setae which medially reaches to the basal third. In the 

 type of genus the following moderately long, stout, 

 oblique bristles present : on the hind femur 1 lateral at 

 the basal third and apparently no others; its tibia has 

 3 well developed, dorsomedial, 2 dorsolateral, 5 ventro- 

 lateral, and 1 dorsolateral bristle. Middle femur with 



