112 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



Genus SIMULIUM Latreille, 1802 

 SIMULIUM (NOTOLEPRIA) EXIGUUM * Roubaud 



SimuKum exigimm Roubaud, Bull. Mus. Nat. Hist. Nat., Paris, vol. 12, pp. 108- 

 iio, 1906 (original description, female). — Vargas, Rev. Inst. Salubr. 

 Enferm. Trop., vol. 3, No. 3, fig. 15, 1942 (? genitalia) ; vol. 4, No. 4, figs. 

 1-9, 1943 (c? genitalia and leg, 5 leg, pupal cocoon and filaments. — Lane 

 AND Vulcano, Rev. Ent., Rio de Janeiro, Brazil, vol. 14, No. 3, p. 437, fig. 

 14, 1943 (buccopharyngeal apparatus). — Dampf, Canadian Ent., vol. jG, pp. 

 1 17-124, 6 figs., 1944 (existence of dichoptic as well as holoptic d'cj'; external 

 features of ? and of both forms of cS, with figures of head, thorax, and of 

 profile of (S genitalia). — Wygodzinsky, An. Inst. Med. Reg. Tucuman, 

 Argentina, vol. 3, No. 2, pp. 214-217, figs. 54-56, 1951 (female). 



Simiilium (Notolepria) exiginmi Roubaud, Vargas, Martinez, and Diaz, Rev. 

 Inst. Salubr. Enferm. Trop., vol. 7, No. 3, pp. 171-172, fig. 153, 1946 (larva). 



Male (pi. 22, figs. 16-18). — 2.0 mm. long. The dimorphism in the 

 males of this species described by Dampf (1944) is common in Guate- 

 mala. In those streams where dichoptic males emerge, almost 20 per- 

 cent of the males are of that form. Dichoptic males have been found 

 in 5 of 79 streams in which exiguum was collected, the localities being 

 in different parts of the country. Since, outside of the facial charac- 

 ters, the principal difference is only one of size, the description below 

 will concern itself with the normal holoptic form. 



Head: Holoptic. Eyes black. Antenna 460 /t long, 11 -segmented, 

 hardly tapering, the eleventh segment wide and blunt; segment 

 3<i+2, 3 = 4 + 5, 3 = 11; scape and pedicel brown, the flagellum 

 black. Palpi dark brown to black. Clypeus black, white-pruinose, 

 irregularly covered with short black hairs. 



Thorax: Mesonotum velvety black, with bluish-white pruinosity 

 on all parts according to the angle of the light source, without definite 

 bands, stripes, or other patterns ; with short, broad, appressed, golden- 

 yellow, scalelike hairs over the mesonotum, more numerous on anterior 

 fourth and in prescutellar region. Humeral angles black, with golden- 

 yellow scales. Scutellum velvety black, with long black hairs and 

 golden-yellow scalelike hairs. Postnotum velvety black, white-pruinose, 

 devoid of hairs. Pleural regions dark brown to black, with shiny white 

 pruinosity. Stem of halter dark brown, the knob brilliant yellow, cup- 

 shaped. Wings, 1.9 mm. long and 0.85 mm. wide; relation of body 

 length to wing, 1:1; Sc pilose along basal fifth ; Ri spiny along the 

 distal half, with occasional hairs among the spines ; R2+3 pilose along 

 distal six-sevenths ; Cuo arcuate ; discal cell absent. 



Legs: Leg i, length, 1.9 mm.; entire leg light brown except the 

 distal half of the basitarsus and tarsal segments 2-5, which are dark 



* See footnote 6, p. 68. 



