66 



UNITED STATES NATIONAL MUSEUM BULLETIN 224 



Genus Margaritola Hull 



Figures 16, 418, 865, 874, 2249 



Margaritola Hull, Proc. Ent. Soc. Washington, vol. 60, p. 255, 

 1958. Type of genus : Margaritola mirabilis Hull, 1958, by 

 original designation. 



Peculiar flies, small and robust with short, rather 

 high thorax, quite wide head with prominent, goggle- 

 eyed appearance. It has exceptionally broad, general- 

 ized wings and a very long antenna composed chiefly 

 of the microplumose microsegments, which are longer 

 than the third segment itself. Length 6 mm. without 

 antenna. 



Head, lateral aspect : The head is of medium length, 

 in profile the upper face is quite short, almost plane 

 with the eye and strongly retreating below. Occiput 

 poorly developed in profile but slightly more prom- 

 inent ventrally and from the ventral aspect the lower 

 eye corners are strongly rounded off, exposing a con- 

 siderable amount of occiput with dense, erect micro- 

 pubescence and deep facial grooves. The proboscis is 

 exceptionally small and short, robust but obtuse, a little 

 compressed laterally and with considerable, fine, apical 

 pile not extended as far as the face. Palpus large, 

 elongate, and cylindrical, with a small, short, bulbous, 

 basal segment ; the second segment has numerous, slen- 

 der, basal, lateral and apical, bristly hairs. Antenna 

 attached at the upper third of the head in profile, but 

 actually rather close to the vertex. The antenna is un- 

 usually elongate, nearly twice as long as the head; it 

 is comparatively slender and of uniform thickness. 

 The first two segments are each quite short, subequal, 

 and beadlike, with fine, short bristles below and above 

 on the second segment, but with setae at the top of 

 the first segment. The third segment, if microseg- 

 ments are included, is at least five times the combined 

 length of the first two segments. The third segment 

 proper is not as long as the two microsegments but 

 nearly as long as the second and ultimate microsegment. 

 The first microsegment is short, its junction with the 

 apical microsegment is not very clearly delimited. 

 Both of them bear, together with the last half of the 

 third segment, very dense, long micropubescence or 

 microplumose pile. 



Head, anterior aspect : The head is quite wide, at least 

 twice as wide as high or a little wider, and due to the ex- 

 pansion of the eyes below and above it presents a some- 

 what goggle-eyed appearance. Face below antenna 

 about one-fourth the head width, very slightly wider 

 below, the upper third bears not very dense, coarse, ap- 

 pressed pubescence. The remainder is polished and 

 bare, except for similar, sparse pubescence bordering the 

 subepistoma which is small and nearly horizontal. 

 Upper face with no pile ; middle face with 2 or 3 long, 

 slender, bristly hairs or weak bristles. Lower, re- 

 treating face with 3 or 4 similar hairs on each side. 

 Front extremely short, wide, mostly bare, slightly wider 

 than the upper face ; it has no pile but ocular pubescence 

 is present. Vertex a little widened, scarcely excavated 



though the eye rises above the vertex. The ocellarium is 

 quite large and rather high, with vertical sides ; it has 

 a large anterior ocellus and 3 short, weak, pale bristles 

 on each side between the ocelli and a minute hair behind. 



Thorax : The thorax is short and rather high ; the 

 mesonotum is moderately high and convex, abrupt an- 

 teriorly, densely covered with coarse, undifferentiated, 

 suberect pile of uniform length over the whole. The 

 surface on the posterior middle portion is granulate. 

 Lateral bristles are absent. Metanotum low but the 

 convex, micropubescent scutellum has a few, scattered, 

 short, discal hairs and no marginal pile except micro- 

 pubescence; it slopes downward considerably. Pro- 

 notum with fine hairs; mesonotum with a few very 

 fine, short hairs. Metapleuron with a vertical band of 

 long, fine hairs. Whole pleuron pollinose; postmeta- 

 coxal area membranous ; lateral metasternum with pile ; 

 prosternum fused laterally. 



Legs : The legs are short, especially the femora. The 

 first 4 are distinctly stout, the hind femur is only mod- 

 erately stout and slightly longer. Hind femur densely 

 covered with rather long, fine appressed pile ; and weak, 

 slender bristles or bristly hairs are present in small 

 numbers. Hind femur with very weak, ventrolateral 

 bristles and with 4 much longer, ventromedial, equally 

 slender bristles. Hind tibia with 2 lateral bristles at 

 the middle, and beyond and in nearly the same position 

 2 ventrolateral bristles and 1 other basal, shorter bris- 

 tle ; also there are 2 ventromedial bristles and 2 others, 

 erect instead of directed forward, near the apex. Ven- 

 trally the apex of the tibia has 4 or 5 weak, straight 

 bristles. Hind basitarsus with dense, erect, glandular- 

 tipped pile. Middle femur with 4 or 5 long, slender 

 hairs ventrally. Tibia with a few weak bristles similar 

 to the hind tibia. There are 2 anterior elements at the 

 middle and beyond, 4 shorter ventral bristles, 5 short, 

 posterior bristles and 3 quite long, more stout, also pale, 

 posteroventral bristles. Anterior femur with a single 

 long, slender bristle at the base ventrally ; the tibia is 

 quite slender and bears 3 or 4 fine, short, posterodorsal 

 bristles, 4 longer, slightly stouter, posteroventral bris- 

 tles, and 3 or 4 short, weak, anterodorsal bristles. Apex 

 of anterior tibia without spine, the distal circlet of bris- 

 tles is subapical. Claws small, straight, sharp and 

 hooked at the immediate apex; pulvillus well devel- 

 oped; the empodium short and somewhat swollen at 

 the base. 



Wings: The wings are exceptionally broad, little 

 more than twice as long as wide; marginal cell quite 

 widely open ; the auxiliary vein and the first vein and 

 the costa are all much stouter than the remaining veins, 

 although the cubitus is also stout. The two branches 

 of the third vein end almost an equal distance above 

 and below the wing apex. The second submarginal 

 cell is rather narrow, at base widened entirely in front 

 of the third vein ; fork of third vein a little beyond the 

 end of the discal cell. All posterior cells open max- 

 imally; medial crossvein and upper intercalary vein 

 of equal length; posterior crossvein long, discal cell 



