NO. I BLACK FLIES OF GUATEMALA — DALMAT 23I 



Genitalia: Sidepiece (pi. 26, fig. 88) rectangular in shape, the 

 width about 1.5 times the length ; dorsal opening occupying about half 

 of dorsal surface of sidepiece. Clasper (pi. 26, fig. 88) much longer 

 than wide, about 1.7 times the length of sidepiece; broader at base 

 than at apex, the middle region somewhat constricted ; apex rounded 

 with a single subterminal spine that is situated within a longitudinal 

 groove ; with very long, troughlike basal process that extends at least 

 to the edge of the dorsal opening of the sidepiece, its terminal margin 

 serrated. Body of adminiculum (pi. 26, fig. 90) subquadrangular, 

 somewhat bonnet-shaped, longer than wide, the apical angles well 

 rounded ; basal processes broad, strongly divergent, with heavy pig- 

 mentation that extends longitudinally across the body of adminiculum 

 on either side of midline ; numerous rather long hairs emerging from 

 circular region near apex of adminiculum. Adminicular arms (pi. 26, 

 fig. 89) with about 15 strong teeth, all of about equal length, emerging 

 in all directions from the axis of the arm ; lateral plate large and tri- 

 angular in shape, with numerous wrinkles. 



Female (pi. 33, figs. 208-210, and pi. 35, fig. 248). — 3.1 mm. long. 



Head: Dichoptic. Eyes black; fronto-ocular triangle very small, 

 its base equal to the height. Antenna 600 fi long, 11 -segmented, 

 slightly tapering ; segment 3<i+2,3<4+5,3>ii; scape and pedicel 

 brown, the flagellum black. Palpi black. Frons black, white-pruinose, 

 with I irregular row of long black hairs along the margins. Clypeus 

 black, white-pruinose, margins irregularly covered with black hairs. 

 Occipital region black, white-pruinose, with long black hairs, Cornuae 

 of buccopharyngeal apparatus sclerotized, with blunt, somewhat ser- 

 rated apex ; median space hyaline, with 4 rows of wide, blunt teeth. 



Thorax : Mesonotum velvety black ; on anterior margin there is a 

 rectangular patch of white pruinosity on either side of midline ; from 

 the inner posterior angle of each patch there extends a longitudinal 

 white-pruinose band that continues posteriorly to the white pruinosity 

 of the prescutellar region, the bands convergent near the middle to 

 form a lyre-shaped design ; midline with narrow stripe of white prui- 

 nosity; lateral margins with band of white pruinosity the anterior 

 limit of which continues around the anterior margin of the scutum, 

 almost reaching the rectangular patches ; long, narrow, yellow, scale- 

 like hairs on mesonotum, more numerous around periphery ; fine black 

 hairs over entire mesonotum, long black ones in prescutellar region. 

 Humeral angles black, with white pruinosity. Scutellum black, with 

 yellow scalelike hairs and long black hairs. Postnotum velvety black, 

 white-pruinose, devoid of hairs. Pleura black, with white pruinosity. 

 Stem of halter brown, the knob tan. Wings, 3.1 mm. long and 1.4 mm. 



