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UNITED STATES NATIONAL MXTSEUJI BULLETIN 22 4 



Genus Ommatius Wiedemann 



FiGUBES 296, 297, 298, 306. 683, 684, 691, 1365, 1366, 1374, 1375, 

 2183, 2239 



Ommatius Wiedemann, Diptera exotica, pt. 1, p. 213, 1821. 

 Tyi)e of genus : Asilus marginellus Fabricius, 1781. Desig- 

 nated by Coquillett, 1910, the first of 3 species. 



Ommatinus Becker, Ent. Mitt., vol. 14, p. 84, 1925. Type of 

 genus: Ommatius pinguis Wulp, 1872. original designation. 

 See comment under subgenus Metommatius, new subgenus. 



Ommatiics lias one subgenus, Metommatius, new sub- 

 genus. 



Small to quite large flies, easily recognized by the 

 pectinate, bristly style of the third antennal segment. 

 The plumes are distributed over the entire length of the 

 style, and present in single or double rows. Length 6 

 to 30 mm. 



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

 the face is short, gradually becoming more prominent 

 below but most of its greater length is due to the reces- 

 sion of the eyes. In some species there is a low, 

 rounded, ventrally retreating eminence on the lower 

 half of the face. The occiput is moderately prominent 

 through the middle of the head ; the lower fifth of the 

 eye is often angularly recessive posteriorly. The occip- 

 ital pile is stiff, abundant below, and sometimes rather 

 fine, with slender bristles which begin near the middle 

 of the head and become only moderately stout near the 

 vertex. The upper occipital bristles are usually 

 strongly proclinate, and sometimes divided on the 

 upper fifth of the head into a group which turns down- 

 ward and another which turns upward. The proboscis 

 is of moderate length, stout and cylindrical, the base 

 swollen and with a transverse, circular crease near the 

 apex ; the apex bears stout bristles ; the sides at the base 

 bear numerous, long hairs. Palpus of one segment with 

 stiff, long pile and terminal bristles. The antenna is 

 attached at the upper third of the head and is short ; the 

 third segment is short and pyriform, with a long, naked 

 style bearing 1 or 2 rows of niunerous plumes through- 

 out its entire length, directed ventrally. 



Head, anterior aspect : Tlie face below the antenna is 

 narrow and usually a seventh to a tenth the head width ; 

 it is rather rarely as wide as a fifth, and always strongly 

 divergent below. Surface of face pubescent, with 

 usually only a very few, scattered hairs on the middle 

 and upper portion and more numerous hairs, sometimes 

 of bristly character, above the epistoma. ISIiddle and 

 upper face sometimes without any bristles, more often 

 with 1 or 2 vertical rows containing from 1 to 6 bristles, 

 slender or stout. Usually there are 1 to 7 transverse 

 rows of stout, long bristles on the recessive portion of 

 the face above the subepistomal area. The subepis- 

 tomal area forms the gently convex, longitudinal, ob- 

 lique ridge on each side and is laterally pubescent; 

 cheeks short. The front is short and pubescent, with 

 parallel sides or slightly convergent; the vertex is gen- 

 erally more narrow, and deeply excavated; the ocel- 

 larium is large, with vertical sides, set quite far to the 



front, leavmg the postvertex with a deeply channeled 

 recess. Ocellarium with a few minute hairs and always 

 a pair of stout, moderately long, postocellar bristles. 



Thorax : The mesonotum is high and sometimes quite 

 high, strongly sloping both anteriorly and posteriorly ; 

 the anterior portion is a little compressed laterally, the 

 surface densely pubescent with scanty, fine, partly 

 setate pile laterally and with a double acrostical row of 

 setae and with dorsocentral bristles differentiated only 

 on the posterior half. Humerus with long pile. The 

 lateral complement of bristles consists of 2 notopleural, 

 rather far apart, 1 or 2 postsupraalar, and 1 postalar ; 

 the thick, convex scutellum is usually without bristles 

 but with a few, scattered, stiff hairs. The propleuron, 

 mesopleuron and upper stemopleuron each bear scat- 

 tered, fine pile; the pronotum sometimes with a few, 

 stout bristles. Posthypopleuron and metapleuron with 

 a row of fine, long, bristly hairs and weak or strong 

 bristles. Pteropleuron with or without pile. Prester- 

 num continuous and fused. Scutellum with or without 

 a distinct impressed rim; the metanotal callosity is 

 bare; the postmetacoxal area forms a wide, complete, 

 chitinized arch behind the postcoxa. 



Legs: The femora are stout but never strongly 

 swollen ; together with the dorsal surface of the tibiae 

 they are densely, appressed setate. Bristles are mod- 

 erately prominent and stout, attenuate and sharp and 

 in some species replaced on the posterior and ventral 

 surfaces of the middle and anterior tibiae by dense rows 

 of long, bristly hairs. Hind femur with 4 to 6 ventro- 

 lateral bristles, as many or more ventromedial bristles ; 

 also with, or without a lateral row of 4 bristles ; the sub- 

 apex has 1 dorsolateral bristle and sometimes 1 apical 

 dorsomedial bristle. Middle femur with 3 or 4 anterior 

 bristles and 1 near the apex posteriorly. Anterior 

 femur generally without bristles but often long, stiff or 

 bristly hairs ventrally. Posterior tibia with 2 or 3 

 dorsolateral bristles and a like ntunber of dorsomedial 

 bristles and 1 ventrolateral bristle beyond the middle; 

 apex with only 6 bristles. Anterior four tibiae usually 

 with only 2 bristles in each row. Claws slender, strongly 

 bent at the apex ; the pulvilli large ; the empodium re- 

 duced in length. 



Wings: The marginal cell is closed and stalked; 

 fourth posterior cell closed with a long stalk, the anal 

 cell closed, the second basal cell ends in two veins which 

 are fused beyond ; the alula is large, the ambient vein 

 complete. The fourth vein or first branch of the medius 

 is dra'rni toward the apex of the wing leaving the second 

 posterior cell rather wide on the margin. The posterior 

 crossvein is longer than the upper section of tlie inter- 

 calary vein and tends to be drawn toward the base of the 

 wing. The costa and the marginal and submarginal 

 cells are often greatly widened, especially along a short 

 portion in the middle of the wing. The costal vein may 

 be very greatly thickened, with the widened portion of 

 the wing strongly rippled. 



Abdomen : Tlie abdomen is cylindrical with nearly 

 parallel sides; the first tergite is wider than the re- 

 mainder and nearly as wide as the mesonotum. Pile of 



