NO. I BLACK FLIES OF GUATEMALA — DALMAT 255 



pronounced apical expansion ; along ventral surface there is a longi- 

 tudinal keel-like structure, extending from the apex to about the 

 center of the adminicular body, clothed with numerous hairs; basal 

 processes well sclerotized, the ends blunt, almost spatulate, with small 

 winglike expansion lateral to each. Adminicular arms (pi. 26, fig. 

 104) with about 11 teeth arranged in linear fashion, half of them being 

 small, the others very large; lateral plate irregularly quadrangular, 

 wrinkled, somewhat sclerotized. 



Female (pi. 33, figs. 223-225, and pi. 35, fig. 258). — 3.1 mm. long. 



Head : Dichoptic. Eyes small, black ; fronto-ocular triangle very 

 small, relation of base to height, 2:1. Antenna 500 /a long, 11 -seg- 

 mented, strongly tapering; segment 3 = 4 + 5, 3>i or 2; scape and 

 pedicel light brown, the flagellum black. Frons white-pruinose with 

 2 rows of black hairs along each margin. Clypeus and occipital region 

 white-pruinose with black hairs. Cornuae of buccopharyngeal appara- 

 tus sclerotized, wide, somewhat shovel-like; median space semicircu- 

 lar, hyaline, without teeth. 



Thorax: Mesonotum black, with 2 longitudinal stripes of white 

 pruinosity, each beginning at the anterior end as an extension of a 

 white-pruinose triangle that is contiguous with the anterior margin 

 of the mesonotum, and ending posteriorly where it blends with the 

 white pruinosity of the prescutellar region ; light-yellow scalelike hairs 

 rather evenly distributed over entire mesonotum ; few long black hairs 

 in prescutellar region. Humeral angles pronounced, white-pruinose. 

 Scutellum black, with yellow scalelike hairs and with long black ones. 

 Postnotum velvety black with white pruinosity, devoid of hairs. 

 Pleura white-pruinose. Stem of halter brown at base and tan apically ; 

 the knob pale yellow, cup-shaped. Wings, 3.1 mm. long and 1.4 mm. 

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

 four-fifths ; Ri spiny and pilose along distal half ; R2+3 pilose except 

 for very small basal section ; Cug arcuate ; discal cell absent. 



Legs: Leg i, length, 2.8 mm.; coxa and trochanter light brown; 

 femur light brown with apical dark ring ; basal two-thirds of tibia tan, 

 apical third black ; tarsus black. Leg 2, length, 3.0 mm. ; coxa and tro- 

 chanter light brown ; femur, tibia, and tarsus as on leg 2. Leg 3, 

 length, 3.5 mm. ; coxa dark brown ; trochanter yellow ; femur light 

 brown with small apical black region ; tibia with basal two-thirds tan, 

 the apical third black; basitarsus tan on basal half, black on apical 

 half ; tarsal segments 2-5 black ; relation of basitarsus to second seg- 

 ment, 4.3 : I ; calcipala small, not reaching pedisulcus ; pedisulcus well 

 developed at middle of second segment ; claw with well-developed basal 

 heel and with submedian tooth (pi. 35, fig. 258). 



