NO. I BLACK FLIES OF GUATEMALA — DALMAT 269 



Abdomen : Tergite of segment i black, with short black hairs ; 

 pleurites black, with long dark hairs reaching segment 5. Tergite of 

 segment 2 black, white-pruinose along anterior margin, with short 

 black hairs ; pleurites white-pruinose. Other segments black ; pleurites 

 of segments 2-4 with long brown hairs. Sternites tan, the midline 

 black. 



Genitalia: Sidepiece (pi. 27, fig. 112) roughly rectangular in 

 shape, wider than long ; dorsal surface with depression near the poste- 

 rior margin near the articulation with the clasper; outer posterior 

 angle protruding noticeably ; dorsal opening occupying less than half 

 of surface of sidepiece. Clasper (pi. 27, fig, 112) long and slender, 

 about one and one-half times the length of sidepiece ; apex rounded 

 with a single strong apical spine. Body of adminiculum (pi. 27, fig. 

 113) quadrangular in shape, wider than long, with apical concavity 

 from which emerge numerous long hairs ; on its ventral surface there 

 is a longitudinal keel-like structure, much wider than in other species, 

 clothed with numerous hairs ; ventral surface of adminiculum with 

 numerous short, stout spines. Adminicular arms (pi. 27, fig, 114) 

 with many teeth, there being about three large conical ones near the 

 base, apical to which there is a mixture of small and large teeth; 

 lateral plates somewhat oval in shape, wrinkled, partially sclerotized. 



Female (pi. 34, figs. 232-234, and pi. 35, fig. 257),— 3,2 mm. long. 



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

 relation of base to height, 1.5 : i. Antenna 580 /x long, 11 -segmented, 

 slightly tapering; segment 3<H-2, 3<4-l-5, 3<ii; scape and pedicel 

 brown, flagellum black. Frons, clypeus, and occipital region black, 

 white-pruinose, clothed with black hairs. Cornuae of buccopharyngeal 

 apparatus only slightly sclerotized, expanded at apices ; median space 

 semicircular, without median concavity, hyaline, and with serrated 

 edge. 



Thorax : Mesonotum velvety black ; white-pruinose patch on either 

 side of midline, contiguous to the anterior margin ; behind each patch 

 there extends posteriorly a longitudinal stripe of white pruinosity 

 which joins with the white pruinosity of the prescutellar region ; very 

 narrow line of white pruinosity along the midline as well ; wide band 

 of white pruinosity along the lateral margins ; numerous long, narrow, 

 bronze-colored, scalelike hairs on mesonotum, especially around the 

 periphery, most concentrated on anterior fourth of scutum; several 

 long black hairs on prescutellar region. Humeral angles brown, with 

 white pruinosity. Scutellum shiny black, with some bronze-colored 

 scalelike hairs and a few long black hairs. Postnotum velvety black, 

 completely white-pruinose, devoid of hairs. Pleura black, white- 



