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UNITED STATES NATIONAL MUSEUM BULLETIN 224 



the first two segments are subequal. The third segment 

 is slightly longer than the first two, no wider, strongly 

 attenuate at the base; it is barely convex dorsally, but 

 strongly convex below and the blunt apex carries a 

 minute, short bristle. 



Head, anterior aspect : The face is extremely narrow 

 on the upper half, about a twentieth of the head width 

 and strongly divergent below; the eye continues to 

 diverge posteriorly. Anterior eye facets enlarged near 

 the middle of the head. The front is small, narrow, 

 pubescent, the vertex not excavated except behind the 

 ocelli ; the ocellarium is large, the posterior eye corners 

 only a little rounded and flared. Upper occiput along 

 the middle near the eye margin with 4 short bristles. 



Thorax : The thorax is exceptionally high and short ; 

 the mesonotum anteriorly overhangs the prothorax 

 slightly and is steeply sloping behind. There is a 

 single, remarkably long, conspicuous, dorsocentral 

 bristle in the middle of the presutural part of the 

 mesonotum and a few other minute, short setae. The 

 notopleuron and the supraalar region each have 1 long, 

 conspicuous bristle; postalar region and the scutellum 

 with none. In contrast to Leptopteromyia Williston, 

 the long, chitinized metasternum with its medial seam 

 is oblique instead of horizontal to the thorax. Halteres 

 on long, slender stalks, forming conspicuous club- 

 shaped bodies at their apices. 



Legs: The hind femur and its tibia quite long and 

 slender; the femur is a little clavate on the distal third, 

 the latter very little thickened distally and both with 

 conspicuous though very slender bristly hairs. This 

 femur bears a medial row of such hairs on the distal 

 third, on the ventrolateral margin and most of the 

 ventromedial margin. Its tibia has 4 such rows ventro- 

 laterally, ventromedially, dorsolaterally, and dorso- 

 medially, each with about 15 elements. Anterior 4 legs 

 with fewer and less conspicuous setae, but the apices of 

 their tibiae each with 1 or 2 long, conspicuous bristles, 

 their first two tarsal segments also with rather long 

 bristles. First four tarsi with the posterior claw re- 

 duced and the hind tarsi with the medial claw more 

 strongly reduced. Pulvilli absent; empodium present 

 but very fine, short, and reduced in length. 



Wings : All the veins are present in the wing ; the first 

 vein extends nearly to the wing apex and rims very close 

 to the costa throughout its length so that the marginal 

 cell is remarkably narrow. Apices of remaining 

 branches of the radius are crowded rather closely to- 

 gether near the wing apex. The anterior branch of 

 the third vein ends nearest the wing apex. Ventral 

 surface of the second vein, both surfaces of both 

 branches of the third vein and all branches of the 

 fourth and fifth vein with long, stout, suberect setae. 

 The alula is absent ; the ambient vein is complete ; the 

 veins beyond the end of the second basal cell are fused 

 for a short distance. 



Abdomen : The abdomen is elongate and very slender, 

 the wings not quite reaching to the end of the third 

 segment ; the first segment is extremely short, the second 



segment is three-fourths as long as the wing and the 

 first three segments are subcylindrical. The pile is 

 scanty, appressed and setate; the first segment bears 

 a few, short bristles laterally. Male terminalia wide 

 but short. 



Distribution: Neotropical: Schildia fragilis Carrera 

 (1944) ; microthorax Aldrich (1923). 



Subgenus Shannomyioleptus Carrera 



FiGUBES 205, 589, 1194, 1203, 1584 



Shannomyioleptus Carrera, Papels Avulsos Dep. Zool., SSo 

 Paulo, vol 4, p. 87, 1944. Type of subgenus: Shannomyio- 

 leptus fragilis Carrera, 1944, by original designation. 



Small, extremely delicate flies with threadlike abdo- 

 men, very much like Schildia Aldrich. I find the only 

 differences to be a moderately longer third antennal 

 segment, to which is attached a small microsegment, and 

 the presence of 1 pair of anterior dorsocentral bristles 

 in Schildia and more than 1 pair in Shannomyioleptus. 

 Length 7 to 8 mm. 



Head, lateral aspect : The face is plane with the eye 

 throughout its length, the small, cylindrical proboscis 

 extends well beyond the face, the occiput is not visible 

 in profile and has a sublateral fringe of fine, bristly 

 hairs with near the vertex a single, slightly longer, 

 slightly more stout element. The palpus has one seg- 

 ment, is minute, short and clavate, with rounded apex. 

 The antenna is attached at the upper fourth of the head, 

 the first two segments subequal, with a few, fine setae 

 above and below; the third segment is about iy 2 times 

 the combined length of the first two, attenuate toward 

 the base, widest in the middle, a little narrowed dis- 

 tally, finely pubescent and bears at the apex a very 

 short style. In Schildia the third segment is approxi- 

 mately the same length as the first two and the style is 

 shorter. 



Head, anterior aspect: The head is considerably 

 wider than the thorax, the face below the antenna is 

 quite narrow and about a fifteenth the head width, and 

 divergent below. The face is pollinose, with an im- 

 pressed medial line which is bare, and at the epistoma 

 it bears 2 long, slender, curved, anteriorly directed, 

 bristly hairs. Front small, pollinose, without pile, 

 with a medial bare spot above the antenna ; the vertex 

 is scarcely excavated ; the ocellarium is small but with 

 vertical sides and without pile. 



Thorax: The mesonotum is rather high, steeply 

 arched posteriorly, produced bluntly forward anteri- 

 orly and overhanging the pronotum. It is polished and 

 bare except for 2 or 3 minute, fine, erect, dorsocentral 

 bristles and likewise anteriorly 1 or 2 still finer, shorter, 

 acrostical hairs. Sides without bristles or hairs. Scu- 

 tellum very small, flat, dully pollinose without pile, 

 hairs or bristles. Beginning along the dorsal surface 

 of the mesopleuron there is a diagonal band of pale 

 pollen or micropubescence and the remainder of the 

 pleuron is similarly covered. Pile absent except for 

 very minute hairs on the metapleuron. The wings are 



