NO. I BLACK FLIES OF GUATEMALA — DALMAT 1 73 



margin light brown. Other segments black, the pleural regions with 

 gray pruinosity. All segments with short brown hairs. Stemites 

 tan-pruinose. 



Genitalia: Sidepiece (pi. 24, fig. 51 A) somewhat rectangular in 

 shape, approximately 1.3 times wider than long, the dorsal opening 

 occupying about one-half its surface. Clasper (pi. 24, fig. 51 A) 2.6 

 times longer than wide, 1.7 times the length of sidepiece; margins 

 of clasper sinuous, well-marked opening on inner surface at base ; 

 apical region much narrower than rest of clasper, the apex itself 

 rounded ; terminal spine single, pointed, a distance from the apex. 

 Both sidepiece and clasper with numerous long, stout, spinelike hairs. 

 Body of adminiculum (pi. 24, fig. 51 B) irregularly rectangular, much 

 wider than long, the apical margin with marked concavity from which 

 arise numerous hairs which are longer than any others on adminicu- 

 lum ; sides of adminiculum with small hyaline expansions ; on ventral 

 surface of body of adminiculum, passing longitudinally along midline, 

 is a low keel which has numerous very short hairs on its ridge and 

 somewhat longer hairs laterally ; remainder of ventral surface with 

 very few hairs, none on lateral expansions ; basal prolongations with 

 their ends well sclerotized and spatulate. Adminicular arms (pi. 24, 

 fig. 51C) with about 28 pointed teeth, parallel to one another and 

 perpendicular to the long axis of the arm ; lateral plate triangular, 

 somewhat sclerotized, and wrinkled. 



Female (pi. 30, figs. 169-171, and pi. 35, fig. 267). — 4.0 mm. long. 



Head : Dichoptic. Eyes reddish brown ; height of fronto-ocular 

 triangle 2.1 times the base. Antenna 750 fi in length, 11 -segmented, 

 slightly tapering ; segment 3<i+2or4 + 5,3=ii; scape and pedicel 

 yellow, the flagellum brown. Palpi brown with black hairs. Clypeus 

 coppery red, with gray pruinosity and golden-yellow hairs. Frons 

 dark reddish brown to black with gray pruinosity and with short, fine, 

 black hairs. Occipital region black, with numerous black hairs and a 

 few white ones. Cornuae of buccopharyngeal apparatus narrow, only 

 slightly indented, with corrugatedlike impressions ; border of median 

 space hyaline, smooth, without teeth. 



Thorax : Mesonotum dark reddish brown, completely gray-prui- 

 nose; small, fine, black hairs and very short, golden-yellow scalelike 

 hairs distributed over entire mesonotum, the scalelike hairs never in 

 groups and somewhat longer in prescutellar region ; long, erect, black 

 hairs on prescutellar region. Scutellum tan, with long, erect, black 

 hairs, shorter recumbent black ones, and several golden-yellow scale- 

 like hairs. Postnotum black with gray pruinosity, devoid of hairs. 

 Pleura black with gray pruinosity. Stem of halter tan, the knob white 



