NO. I BLACK FLIES OF GUATEMALA DALMAT 167 



small transverse region, immediately posterior to anterior fourth, 

 with golden-yellow scales, shorter than the silvery- white ones ; poste- 

 rior fourth with few silvery scales, longer than those on other parts 

 of the notum. Postnotum reddish brown, covered with silvery prui- 

 nosity, and devoid of hairs or scales. Scutellum dark brown, with 

 numerous silvery scales, similar to those on posterior part of meso- 

 notum, and with several long, fine, black hairs. Pleura evenly gray- 

 pruinose. Halteres with tan stem and pale-yellow knob. Wings, 3.7 

 mm. long ; relation of body to wing, i : i ; Sc pilose at least along basal 

 half, usually with a single hair near apical extremity ; Ri pilose only 

 along distal half; R2+3 simple, pilose except for small bare region at 

 base ; Cua arcuate ; discal cell absent. 



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

 yellow except for minute brown patch on ventral surface near the 

 apex ; tibia pale yellow on basal two-thirds of ventral face, the same 

 region on dorsal face black ; apical third completely black ; tarsus 

 black. Leg 2, length, 3.4 mm. ; coxa dark brown, trochanter yellow ; 

 femur yellow with apical dark ring ; tibia with apical half black, the 

 basal half divided into light, dark, and light patches ; basal two-thirds 

 of basitarsus and basal fourth of second tarsal segment yellow, the 

 apical parts of these segments, and all other tarsal segments, black. 

 Leg 3, length, 4.1 mm. ; with same color patterns as on leg 2 ; relation 

 of basitarsus to second joint, 6:1. Calcipala well developed, reaching 

 only halfway to pedisulcus ; pedisulcus well developed one-third dis- 

 tance from base of second segment ; heel well developed with strong 

 secondary spur just apical to it (pi. 35, fig. 237). 



Abdomen : Tergites of first and second segments light brown with 

 white pruinosity, all others velvety black ; pleural regions of first seg- 

 ment black with posterior fringe of yellow hairs. Second through 

 seventh segment with tan-pruinose pleura ; eighth segment with pleura 

 black. Sternites evenly tan-pruinose. 



Genitalia: Cercus (pi. 30, fig. 166) higher than long (wide), 

 posterior margin rounded, clothed with many strong hairs and nu- 

 merous minute, spinelike hairs. Anal lobe (pi. 30, fig. 166) ribbonlike, 

 with ventral extremity curved around border of cercus and with a 

 similar investiture of hairs as on cercus. Genital rod (pi. 30, fig. 168) 

 with short basal dilatation, triangular in shape ; apical expansions tri- 

 angular ; the interior basal angle with a secondary hollow, conical, 

 heavily sclerotized spur extending from it at an angle ; outer basal 

 angle pronounced but with apex blunted ; the apical angle heavily 

 sclerotized and rather sharply pointed ; hyaline, winglike expansions 

 on outer margin of each of the 2 triangles near its apex ; 2 branches of 



