NO. I BLACK FLIES OF GUATEMALA — DALMAT 165 



in prescutellar region, never in regular groups ; fine black hairs evenly 

 spaced over entire mesonotum, these being longer and stouter in 

 prescutellar region. Scutellum yellowish to reddish brown, with 

 golden-yellow scales on both sides, the scales being so numerous that 

 the entire structure appears golden ; several long, slender, erect, black 

 hairs also present. Postnotum yellowish brown, with triangular patch 

 of grayish pruinosity on either side of the midline, contiguous with 

 the anterior margin ; devoid of hairs. Pleura evenly gray-pruinose. 

 Halteres with brown stem and yellow knob. Wings, 3.5 mm. long; 

 Sc pilose along basal third ; Ri pilose along slightly more than its 

 distal half, the hairs intermixed with stouter spines; R2+3 simple, 

 pilose except for small basal region which is bare ; Cu2 arcuate ; discal 

 cell absent. 



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

 yellow, with very small dark patch apically on dorsal and ventral 

 sides ; tibia with small basal yellow ring, followed by black ring, then 

 a central dark-brown region, and finally a terminal black ring ; tarsus 

 completely black. Leg 2, length, 3.1 mm. ; coxa dark brown, tro- 

 chanter yellow ; femur yellow with apical dark-brown ring ; tibia same 

 as for leg i ; tarsus with all segments black except the basal half of 

 basitarsus and a very minute basal section of second tarsal segment, 

 which are yellow. Leg 3, length, 3.7 mm. ; coxa and trochanter with 

 same coloration as on leg 2 ; femur yellowish brown with dark-brown 

 apical ring; tibia broad, dark brown except for very small yellow 

 basal section and a black ring adjacent to it ; tarsus with same color 

 pattern as on leg 2 ; relation of basitarsus to second joint, 4.7 : i ; 

 calcipala and pedisulcus well developed. 



Abdomen : Tergite of first segment light brown, the pleurites black 

 and completely clothed with very long, tan-colored hairs ; second seg- 

 ment black, the tergite covered with white pruinosity ; all other ter- 

 gites velvety black with median patch of gray pruinosity, and clothed 

 with short black hairs, evenly distributed over the surface ; segment 7 

 with gray pruinosity along anterior margin of the pleurites. Sternites 

 brown with central longitudinal black band. 



Genitalia : Sidepiece (pi. 24, fig. 49) almost square, very slightly 

 wider than long ; dorsal opening large, quadrangular, with its angles 

 directed toward each of the margins of the sidepiece. Clasper (pi. 24, 

 fig. 49) much longer than wide, with large bulge on inner margin ; 

 well-marked opening on interior face at base ; apex of clasper some- 

 what truncate ; 2 apical spines, one more terminal than the other, 

 arise along an oblique line, apparently formed by a large concentration 

 of short spinelike hairs. Body of adminiculum (pi. 24, fig. 50) much 



