NO. I BLACK FLIES OF GUATEMALA — DALMAT 259 



midregion. Pleura brown, white-pruinose. Stem of halter light brown, 

 the knob tan. Wings, 3.4 mm. long and 1.4 mm. wide; relation of 

 length of body to wing, 1.2: i ; So pilose along its basal sixth; Ri 

 pilose and spiny along its distal half; R2+3 pilose except for a very 

 short basal section ; Cu2 arcuate ; discal cell absent. 



Legs : Leg i, length, 3.3 mm. ; coxa and trochanter yellow ; clothed 

 with numerous, somewhat appressed, golden-yellow hairs ; femur yel- 

 low with small apical black ring, clothed with both golden-yellow hairs 

 and long black ones ; tibia yellow with a complete black ring around its 

 apical fourth and with most of its inner face black, the outer face 

 silvery-pruinose with short silvery hairs; tarsus completely black. 

 Leg 2, length, 2.9 mm. ; coxa black ; trochanter yellow with its apex 

 somewhat darker ; femur and tibia as on leg i ; tarsus black except for 

 basal half of basitarsus which is yellow. Leg 3, length, 3.7 mm. ; coxa 

 black ; trochanter yellow ; femur as on legs i and 2 ; tibia black except 

 on its basal fourth and along the basal three-fifths of its inner edge 

 where it is yellow ; basal third of basitarsus and of second tarsal seg- 

 ment yellow, the remainder of these segments, as well as all of tarsal 

 segments 3-5, black ; relation of basitarsus to second segment, 4.2 : i ; 

 calcipala well developed, not reaching pedisulcus ; pedisulcus well de- 

 veloped at middle of second segment. 



Abdomen : Tergite of segment i brown ; pleurites black with many 

 long black hairs reaching the fourth segment. Segment 2 with its 

 tergite black, the pleurites dark brown, anterior margin of anterior 

 segment white-pruinose. Other segments black, the pleural regions of 

 segments 5-7 with patch of white pruinosity ; extending laterally from 

 each of the pleurites of segments 2-5 is a tuft of black hairs, shorter 

 than those on segment i ; all tergites evenly clothed with very short 

 black hairs. Sternites tan, the midregion brown. 



Genitalia: Sidepiece (pi. 27, fig. 106) irregularly quadrangular 

 in shape, wider than long, with well-developed dome-shaped expan- 

 sion from outer posterior angle ; dorsal opening broadly quadrangular. 

 Clasper (pi. 27, fig. 106) long and narrow, its length about six times 

 the width ; apex blunt and somewhat curved, with strong spine arising 

 from longitudinal furrow near distal end. Body of adminiculum (pi. 

 27, fig. 107) somewhat rectangular in shape, wider than long, with 

 apical concavity and with longitudinal keel-like structure on its ventral 

 surface ; concavity and keel-like structure clothed with numerous hairs ; 

 entire ventral surface of adminiculum clothed with minute, appressed 

 hairs ; basal processes long, almost equaling the body of adminiculum 

 in length, heavily sclerotized, the apices somewhat pointed; at the 

 middle of the outer margin of each basal process is a small, winglike 



