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UNITED STATES NATIONAL MUSEUM BULLETIN 224 



Text-Figure 26. — Pattern of distribution of the genus Atomosia 

 Macquart. 



Genus Atomosia Macquart 



Figuees 223, 229, 637, 1309, 1318, 2110, 2121, 2122, 2123, 2153, 2156 



Atomosia Macquart, Dipteres exotiques, vol. 1, pt. 2, p. 73, 1838. 



Type of genus : Atomosia incisuralis Macquart, 1838. 



Designed by Coquillett, 1910, the fourth of 6 species. 

 Cormanste Walker, Insecta Saundersiana, vol. 1, pt. 2, p. 154, 



1S51. Type of genus : 

 by monotypy. 



Cormansis halictides Walker, 1S51, 



Small, short and robust flies of bare aspect and short, 

 scanty, appressed pile. The antenna is elongate and 

 always slender. Several abdominal tergites usually 

 bear lateral bristles and the apex of the abdomen in 

 both sexes is strongly cupped, concealing the genitalia. 

 The coloration is always dark, the legs sometimes pale. 

 It is separated from its near relative, Cerotainia 

 Schiner, by the convergent vertex. Length 5 to 12 mm. 



Head, lateral aspect: The head is short, the face 

 very short, except on the lower fourth, where it is 

 slightly elevated and also rendered more conspicuous 

 because of the recession of the eye. Height of face 

 reduced on account of the long, oblique, convex sube- 

 pistomal area. The occiput gradually widens from 

 the upper fourth to the bottom of the eye because of 

 the gradual recession of the eye; occipital pile com- 



posed of fine, scattered hairs ventrally, weak bristles 

 above the middle of the head and with a small cluster 

 of moderately stout bristles on each side behind the 

 postvertex. Proboscis short, robust, tapered from the 

 base and the base sometimes strongly swollen. The 

 proboscis does not extend beyond the face and in some 

 species may not reach to the epistoma. Palpus minute, 

 especially the first segment; the second segment is 

 slender and cylindrical, with a few apical, ventral, and 

 lateral bristles. Antenna attached slightly above the 

 middle of the head, elongate, longer than the head and 

 sometimes nearly twice the head length. The first 

 segment is 1 or 2 times as long as the second, usually 

 slender. The third segment is iy 2 to nearly 2 times 

 the length of the first two segments; it bears at or 

 beyond the middle a dorsal incision of varying depth 

 carrying a distinct spine. The apex is rounded. The 

 first two segments have stout, bristly pile ventrally and 

 sometimes have a fairly long bristle ventrally in the 

 middle of the first segment. 



Head, anterior aspect: The head is as wide as the 

 thorax. The face is comparatively narrow with paral- 

 lel sides, densely micropubescent with coarse, scattered, 

 bristly hairs on the upper part and sometimes a sub- 

 medial, vertical row of 2 or 3 bristles of varying sizes. 

 Epistoma with or without a row of longer, stout bris- 

 tles. Similar, more slender elements are usually con- 

 tinued down the side of the subepistoma. Front 

 strongly divergent and more strongly convergent at the 

 vertex. Sides of the front slanting, leaving below a 

 shallow, longitudinal groove. Front pubescent with a 

 row of stiff hairs near the eye margin and sometimes 

 weak bristles. Ocellarium small but with vertical sides 

 and a pair of stout bristles and sometimes additional 

 postocellar bristly hairs. 



Thorax: The mesonotum is low and rather long, 

 shining, with comparatively abundant, curled, ap- 

 pressed, short, bristly pile. Acrostical elements are not 

 differentiated, the dorsocentral elements are very fine 

 but longer and easily overlooked. Lateral bristles are 

 stout, with the following complement: 1 notopleural, 

 1 supraalar, 1 or 2 postalar, and 1 or 2 pairs on the 

 scutellar margin. Anterior pronotum with 5 or 6 pairs 

 of stout or slender bristles, the remainder of propleu- 

 ron with stiff or bristly pile including the cervical 

 sclerite. Presternum fused and continuous; whole of 

 the mesopleuron and the upper sternopleuron and some- 

 times the anterior hypopleuron with pile. Metapleuron 

 with a vertical band of remarkably long, slender, dis- 

 tally curved bristles and bristly hairs. Lateral meta- 

 notal callosity with an extensive patch of both stout 

 and weak bristles. Metasternum pilose throughout, 

 postmetacoxal area with a complete chitinized arch. 

 Posterodorsal corner of mesopleuron with a stout 

 bristle. 



Legs: All the femora are stout and comparatively 

 little swollen ; the hind femur is a little more swollen 

 distally. The pile is scanty, fine, and subappressed 

 dorsally. The ventral surface of the hind femur and 

 hind tibia each have a dense, conspicuous, somewhat 



