NO. I BLACK FLIES OF GUATEMALA — DALMAT 187 



Genitalia: Sidepiece (pi. 24, fig. 58) almost square, the dorsal 

 opening well formed, quadrangular. Clasper (pi. 24, fig. 58) much 

 longer than wide, about one and one-half times length of sidepiece, 

 with large bulge on outer margin and smaller one on inner margin ; 

 longitudinal ridge on dorsal surface which is accentuated by numerous 

 small spines ; apex much narrower than rest of clasper, with 2 pointed 

 terminal spines, a heavy one somewhat removed from apical margin, 

 and a very small one closer to the margin. Body of adminiculum 

 (pi. 24, fig. 59) almost twice as wide as long, without apical pro- 

 longation or concavity but with very high longitudinal keel on the 

 midline of the ventral surface ; keel and entire ventral surface invested 

 with numerous hairs ; basal prolongations long, well sclerotized, 

 spatulate. Adminicular arms (pi. 24, fig. 60) with approximately 13 

 blunt teeth arranged in linear fashion ; lateral plate somewhat tri- 

 angular in form, very slightly sclerotized. 



Female (pi. 31, figs. 178-180, and pi. 35, fig. 240). — 3.5 mm. long. 



Head : Dichoptic. Eyes black ; height of fronto-ocular triangle 

 equal to the base. Antenna 560 fx long, 11 -segmented, tapering; seg- 

 ment 3 = 4-1-5 = 11; scape and pedicel light brown, segments 3-8 

 brown, segments 9-11 very dark brown. Palpi brown. Frons light 

 brown, with white pruinosity and several black hairs arranged in 2 

 rows along each lateral margin. Clypeus light brown, with white 

 pruinosity and many long black hairs. Occipital region brown, with 

 white pruinosity and clothed with black hairs. Cornuae of bucco- 

 pharyngeal apparatus narrow, somewhat blunt, with membranous 

 extensions on their inner margin ; median space hyaline, without teeth. 



Thorax : Mesonotum grayish black, completely white-pruinose, 

 without designs ; relatively long, yellow, scalelike hairs evenly cover- 

 ing all of mesonotum, in groups of 2-5 ; short, black hairs sparsely 

 but evenly covering all of mesonotum, these hairs longer in prescutel- 

 lar region. Humeral angles white-pruinose, with several short brown 

 hairs. Scutellum tan, with several yellow scalelike hairs and long black 

 hairs. Postnotum velvety brown, white-pruinose, without investiture 

 of hairs of any kind. Pleura white-pruinose. Stem of halter light 

 brown, the knob tan, cup-shaped. Wings, 3.4 mm. long and 1.4 mm. 

 wide ; relation of length of body to wing, i . i : i ; Sc pilose along basal 

 four-fifths ; Ri completely pilose, its distal half also with spines ; R2+3 

 completely pilose ; Cug arcuate ; discal cell absent. 



Legs: Leg i, length, 3.9 mm.; coxa, trochanter, and femur tan; 

 basal third of tibia tan, the remainder dark brown ; tarsus brown to 

 black, with very few long black hairs. Leg 2, length, 3.5 mm. ; coxa 

 brown; trochanter tan; femur brown, with very small basal light 



