NO. I BLACK FLIES OF GUATEMALA — DALMAT 185 



Head : Yellow ; design on frons-clypeus (pi. 40, fig. 373) approach- 

 ing a triangle in shape, the apex being rounded ; from the apex to the 

 base there is a longitudinal dark stripe, and a smaller dark patch on 

 either side of the stripe near its midregiou ; epicranial plates somewhat 

 darker than base color of frons-clypeus, with about 6 dark-brown 

 patches distributed on their posterior half (pi. 40, fig. 373). Each 

 cephalic fan with 54 pectinate branches ; small hairs of each branch 

 are both simple and bifid, not very close together, at regular intervals 

 interspersed with longer, heavier bifid hairs. Mandible with 2 well- 

 defined, pointed teeth on its inner margin, the more distal one twice 

 the length of the other. Antenna 460 fi long, light brown, 4-segmented, 

 the first two segments and one-quarter of third reaching apex of the 

 basal stalk of cephalic fan; segment i<2>3 ; segment 2 with 2 super- 

 ficial divisions also marked by white patches; segment i with longi- 

 tudinal wrinkles ; no segments with transverse striations. Submentum 

 with 9 triangular, sharp, apical teeth, the central one and two outer 

 ones being largest ; ventrolateral row composed of 8 hairs, the seven 

 apical ones trifid near their apices, the basal one bifid ; lateral margin 

 of submentum with 6 teeth, five in a regular sequence, the most-basal 

 tooth somewhat removed from the others. Occipital cleft dome- 

 shaped, the apex with fingerlike prolongation (pi. 42, fig. 410). 



Thorax and Abdomen: Pseudopod (thoracic proleg) with 35-40 

 rows of hooks on its apex; postclypeal sclerites well sclerotized, 

 separated from each other. Posterior sucker with 260-265 ''ows of 

 hooks. Anal gills composed of 3 main branches, the central one with 

 19 fingerlike projections, the two lateral branches each with 20 such 

 projections, giving a total of 59 projections in all. The X-shaped 

 sclerite is simple, well sclerotized, without pigmented patches; no 

 rectal scales or spines but with several extremely small spines on each 

 side between the anterior and posterior arms. No ventral papillae or 

 plaques on eighth segment. 



Types. — Holotype (J*), in the collection of the Instituto de Salu- 

 bridad y Enfermedades Tropicales, Mexico City ; collected in Temixco, 

 Morelos, Mexico, at 1,400-1,500 meters above sea level, November 

 21, 1943. 



SIMULroM (DYARELLA) MEXICANUM Bellardi 



Simulium mexicanum Bellardi, Saggio di Ditterologia Messicana, vol. 2 (Ap- 

 pendix), p. 6, 1862 (original description, male).— Malloch, U. S. Dept. 

 Agr. Bur. Ent. Techn. Ser., No. 26, pp. 35-36, pi. 2, fig. 6, 1914 (female).— 

 Bequaert, in Strong, Sandground, Bequaert, and Ochoa, Contr. No. 6, Dept. 

 Trop. Med. and Inst. Trop. Biol, and Med., Harvard Univ., pp. 216-217, fig. 

 99, 1934 (? and pupa).— Vargas, Rev. Inst. Salubr. Enferm. Trop., vol. 3, 



