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TOUTED STATES NATIONAL MUSEUM BULLETIN 22 4 



Text-Figure 8. — Pattern of distribution of the genus Dioctria Meigen. 



ment one is longer than the second; third segment, 

 including microsegment, as long or longer than the hrst 

 two segments combined and of approximately the same 

 width. Third segment subcylindrical, slightly nar- 

 rowed at the apex, and bearing a long, wide apically 

 rounded, pubescent, spoon-shaped microsegment, which 

 carries a distinct basal spine. First two segments with 

 numerous, appressed, stiff, rather long bristles both on 

 the dorsal and ventrolateral surfaces; third segment 

 with several appressed, dorsal bristles. In some species 

 the first two segments may be nearly equal in length ; in 

 subgenus Eudioctria the antennae are still elongate, 

 though all segments are reduced, including the third. 

 Head, anterior aspect: Face between antennae one- 

 fourth the head width and slightly divergent below; 

 subepistomal area large, slightly oblique or rarely small 

 and strongly oblique. Face micropubescent laterally 

 and below, but often bare beneath the antenna and in 

 the middle of the face; pile absent and bristles con- 

 fined to a rounded cluster covering the lower facial 

 eminence, containing more than 20 stout, curved 

 bristles, or with only a single transverse row of 4 pairs. 

 Front generally very short, polished and bare, in 

 Eudioctria pollinose with a conspicuous row of rather 

 long slender bristles along the ocular margin. Vertex 

 moderately excavated ; ocellar protuberance high with 



steep sides, and a few minute, short, anteriorly directed 

 bristles confined to the posterior region, or in Eudioc- 

 tria with 4 or 5 pairs of long, slender, central bristles. 

 Eye facets at most slightly enlarged. 



Thorax: Low, gently curved, shining, often with 

 pubescent vittae. Pleuron chiefly shining, with spots 

 or diagonal bands of appressed pubescence. Pile of 

 mesonotum rather scanty, erect and bristly ; acrostical 

 band present; dorsocentral bristles moderately distinct 

 but rarely long. In the type of the genus the following 

 complement of long, slender bristles present : One noto- 

 pleural, 7 supraalar, 8 to 10 short postalar, no scutellar 

 bristles. Scutellum flat, its margin often with a wide 

 band of fine bristly hair and similar discal hair or disc 

 bare. The margin almost without pile in Dioctria al- 

 bius. In the type of genus the pleuron anteroventrally 

 has a tuft of long stout curved bristles ; in Eudioctria 

 with pile oidy. Pronotal collar sometimes with 

 bristles. Typically the posterior margin of the meso- 

 pleuron has a vertical row of weak bristles ; metapleu- 

 ron with 6, 7, or 8 bristles; remainder of pleura apilose. 

 Metanotal callosity pubescent only. Ventral and 

 lateral metasternum with pile; postmetacoxal area 

 membranous. 



Legs: All the femora moderately lengthened, the 

 hind femur not quite twice as wide distally as basally. 



