408 



UNITED STATES NATIONAL MUSEUM BULLETIN 224 



Genus Oidardis Hermann 



Figures 218, 677, 1260, 1269 



Oidardis Hermann, Nova Acta Acad. Caes. Leop.-Carol., vol. 96, 

 p. 76, 1912. Type of genus : Oidardis gibbosa Hermann, 

 1912, by original designation. 



Small, black flies with a narrow face and with front 

 and vertex divergent. The face is scarcely or not at all 

 visible in profile even ventrally and bears in vertical row 

 on each side 3 long, slender bristles on the lower face. 

 The antenna is shorter than in most allied genera and 

 the third segment more stout or of greater breadth, with 

 a comparatively blunt apex and no microsegment ; this 

 segment does bear subapically a minute, nascent spine, 

 which is also subdorsal and therefore does not appear 

 from a profile view. The mesonotum is rather shorter 

 and more humped than in other Atomosini ; the genus 

 is probably related to Ewmecosoma Schiner. The ab- 

 domen is relatively broad and short and with the meso- 

 notum lacks punctures. Length 7 to 8 nun. 



Head, lateral aspect: The head is short, strongly con- 

 vex anteriorly but plane posteriorly except the lower 

 corner, which is broadly rounded. Face scarcely visible 

 in profile but very slightly elevated on the lower fourth. 

 The occiput is rather narrow ; the upper part has a deep 

 medial row of 10 or more rather stout bristles ; the upper 

 6 bristles are a little more stout and black. The pro- 

 boscis is relatively slender, slightly compressed later- 

 ally, of uniform width in profile; the apex is bluntly 

 rounded and bears a tuft of long, yellow pile below; 

 at the base is a single pair of ventral, very long, mod- 

 erately stout bristles. Palpus small, cylindrical, of two 

 segments; basal segment with 7 long, pale hairs; apical 

 section with 1 ventral and 3 yellow, apical hairs. The 

 antenna is barely longer than the head; the first two 

 segments are subequal and each bears a single, long, 

 stout, black bristle arising from the middle below. The 

 second segment has 2 unusually long, stout, black bris- 

 tles dorsally and apically ; other short, black bristles are 

 found apically on both segments. Third segment is 

 li£ times as long as the first two segments combined; 

 at its middle it is slightly wider than the second seg- 

 ment and it is obliquely dorsally truncate at apex; the 

 apex may bear ventrally an extremely minute, short 

 spine, or subapically above, lying laterally and subdor- 

 sally there may be a minute, nascent spine. 



Head, anterior aspect : The face is narrow, less than 

 an eighth the head width below the antenna; it is 

 entirely micropubescent and is very slightly divergent 

 below. Pubescence along eye margin longer but rather 

 appressed. The lower and slightly elevated part of the 

 face bears 3 or sometimes 4 pairs of strong, long, an- 

 teriorly directed bristles arranged vertically on each 

 side. Also, there is a long, fine, curved hair at the ex- 

 treme lower lateral corner of the eye. Upper face with 

 3 or 4 short, pale hairs. Sides of front with a single, 

 black bristle. Both front and vertex are divergent. 

 The vertex is only moderately excavated ; ocellar pro- 

 tuberance no higher than upper eye margin, with slant- 



ing sides and bearing a pair of moderately long, stout, 

 black bristles divergent, and curved backward. An- 

 terior ocellus enlarged; anterior eye facets strongly 

 enlarged. 



Thorax : The mesonotum is everywhere appressed, 

 fine, yellowish pilose including the flat humerus. The 

 lateral bristles are long, strong and black and consist 

 of 1 notopleural, 1 supraalar, 1 postalar, and 2 pairs 

 of scutellar bristles on the margin. On the mesopleuron 

 are 36 bristles; on the hypopleuron a few, long hairs. 

 Metapleuron with a vertical band of 10 to 12 quite long, 

 downwardly curved, slender, yellowish to brownish 

 bristles. Slopes of metanotum with abundant pile. 

 Lateral metasternum pilose and postmetacoxal region 

 short and chitinized. 



Legs : The hind femur short, stout, with dense, black 

 appressed pile above and with long, stout, lateral, black 

 bristles, 1 near base and 1 subapical; and also there is 

 a dorsal pair of divergent bristles near apex. Ventro- 

 laterally there is a row of 15 rather long, slender, bristly 

 hairs which are numerous near apex. The ventral mar- 

 gin submedially has 2 rather long, slender, yellow, erect 

 hairs, 1 at base, 1 at middle and the ventral margin also 

 bears numerous, moderately long, erect, yellow hairs 

 consisting of 45 on distal half and about 15 on the basal 

 half. The distal hairs are slightly spatulate or widened 

 apically. Posterior tibia with vei-y abundant, similarly 

 erect, spatulate pile from base quite close to the apex, 

 the apices of pile slightly curled; the extreme, ventral 

 apex of tibia with the usual dense, flat appressed mat 

 of pile in several ranks. Hind tibia with 3 long, slender, 

 ant ero ventral, yellow bristles, besides 1 weak and 1 

 long, strong, lateral, curved, black bristle with the long 

 element placed in the middle. Apex with 2 lateral and 

 1 ventral bristle ; first two segments of tarsus with 2 long 

 bristles, 1 dorsal and 1 medial, and 3 very stout, shorter, 

 lateral bristles. Middle femur with long, stout, antero- 

 basal bristle; a shorter, stout, anteroapical bristle and 

 a pair of dorsoapical bristles. Middle tibia with ex- 

 tremely long anterodorsal and anteroventral, black 

 bristles, 2 above, 3 below; the lower elements are 

 strongly oblique; the ventral surface is beset with 

 numerous, erect, shorter, stiff hairs; first two segments 

 of tarsi with long, apical bristles, the first segment also 

 with a long posterobasal bristle. 



Anterior femur with a stout bristle near the middle 

 posteriorly; its tibia has 3 long, slender, posterior 

 bristles and 1 long, ventral, subapical bristle. Apex 

 with long bristles, 2 dorsal, 2 posterior, 2 anterior, 3 

 ventral. Anterior basitarsus similar to middle tarsus. 

 Pul villi nearly as long as claws; empodium fine, long 

 and slender. 



Wings: Marginal cell closed with a long stalk. 

 Fourth posterior cell closed with a very short stalk. 

 Veins closing fourth posterior cell and discal cell offset 

 by one-half the end of discal cell or less and this 

 comiecting vein is oblique in position. End of fourth 

 posterior cell slightly oblique. End of the second basal 

 cell with 3 veins, the middle vein short. Anal cell 

 with moderately long stalk. Alula narrow but convex ; 



