NO. I BLACK FLIES OF GUATEMALA DALMAT I83 



of buccopharyngeal apparatus well sclerotized, flanged along the 

 borders, with numerous impressions ; median space dentate, but not 

 sclerotized or pigmented. 



Thorax : Mesonotum reddish brown ; on either side of midline, 

 with its base on the anterior margin of mesonotum, is a white-pruinose 

 triangle, its apex extending posteriorly in the form of a white stripe 

 which blends with the pruinosity of the prescutellar region ; wide band 

 of white pruinosity along the lateral margins and another thin stripe 

 along the midline; long, narrow, yellow, scalelike hairs on entire 

 mesonotum and in prescutellar depression, not in groups ; several long 

 black hairs in prescutellar region. Humeral angles shiny brown. 

 Scutellum shiny brown, with numerous long black hairs. Postnotum 

 velvety brown with white pruinosity. Pleura brown with white prui- 

 nosity. Stem of halter light brown, the knob tan to white. Wings, 

 3.5 mm. long and 1.4 mm. wide ; relation of length of body to wings, 

 1.2 : I ; Sc pilose along its basal fifth ; Ri with hairs and spines along 

 apical three-fifths ; R2+3 pilose except for basal sixth ; Cua arcuate ; 

 discal cell absent. 



Legs: Leg i, 3.6 mm.; coxa and trochanter yellow; femur yellow 

 with apical brown band ; median part of tibia yellow, the basal and 

 apical regions dark brown to black ; tarsus black. Leg 2, 3.3 mm. ; 

 coxa black ; trochanter yellow ; femur yellow with apical dark ring ; 

 tibia as for leg i ; basal four-fifths of basitarsus and basal third of sec- 

 ond segment yellow, the remainder of these segments, as well as all 

 other tarsal segments, black. Leg 3, 3.8 mm.; coxa, trochanter, and 

 femur as for leg 2 ; tibia with middle region yellow, apical fourth 

 black ; the basal fourth divided into very narrow yellow ring followed 

 by wider black band ; tarsal colors as for leg 2 ; relation of basitarsus 

 to second segment, 4.5 : i ; calcipala well developed, broad, almost 

 reaching pedisulcus ; pedisulcus very well developed, deep ; claw with 

 basal heel well developed, a sharp secondary spur just beyond the heel 

 (pi. 35, fig. 239). 



Abdomen : Tergite and pleurites of segment i black, covered by 

 white pruinosity, the pleurites with long black hairs. All other seg- 

 ments dark brown to black, with white pruinosity on posterior margin. 



Genitalia: Cercus (pi. 31, fig. 175) higher than long (wide), 

 somewhat rectangular in shape, clothed with many long hairs and with 

 numerous fine, spinelike ones. Anal lobe (pi. 31, fig. 175) narrow 

 at its dorsal end, extending around the cercus, with very wide mem- 

 branous structure ventrally; investiture similar to that of cercus. 

 Genital rod (pi. 31, fig. 177) with basal dilatation in form of triangle; 

 apical expansions of arms of genital fork triangular in form, the apex 



