164 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



the lateral margin, is far removed from the more apical four. Occipital 

 cleft dome-shaped, broad, the apex with convexity (pi. 42, fig. 407). 



Thorax and Abdomen : Pseudopod (thoracic proleg) with 28-34 

 rows of hooks at its apex ; postclypeal sclerites light brown, small, but 

 clearly visible. Posterior sucker with 68-70 rows of hooks. Anal gills 

 consisting of 3 main divisions, each with from 3 to 6 fingerlike pro- 

 jections. Anterior arms of X-shaped sclerite short, poorly sclerotized, 

 completely covered by wedge-shaped patches that extend along the 

 outer margins from the union with the posterior arms to the anal 

 orifice ; patches longer and narrower than those of callidum; the 

 patches of both anterior arms are bridged by a median patch ; posterior 

 arms well developed and heavily sclerotized; no rectal scales. Two 

 extremely minute ventral papillae on eighth segment, hardly visible 

 on some specimens ; no sclerotized plaques. 



Types. — Holotype (c^) and allotype (5), part on slides, the rest 

 on pins, and paratype (^(^, $?, and pupae in the collection of the 

 Instituto de Salubridad y Enfermedades Tropicales, Mexico City; 

 collected from the Rio Sedeno, Veracruz, Mexico, August 1945. 



SIMULIUM (DYARELLA) ACATENANGOENSIS Dalmat 



10 



Simulium (Dyarella) acatenangoensis Dalmat, Ann. Ent. Soc. Amer., vol. 44, 

 No. I, pp. 31-38, figs. 1-8, 1951 (original description, ^, $, and pupa). 



Male (pi. 24, figs. 49-51). — 3.4 mm. long. 



Head: Holoptic. Eyes dark reddish brown. Antenna ii-seg- 

 mented, only slightly tapering; scape and pedicel reddish yellow, the 

 flagellum dark brown ; clothed with short yellow hairs ; segment 

 3<4-l-5, 3 = 1-1-2, 3>ii. Palpi reddish brown at base, black along 

 the remainder of their length. Clypeal region white-pruinose. Oc- 

 cipital region with white, erect hairs. 



Thorax : Mesonotum velvety black, with reddish cast in dried 

 specimens ; when viewed from above, with the head directed forward 

 and downward, and with the light source from in front at a 45 ° angle 

 to the specimen, there is seen on either side of the midline a narrow 

 longitudinal band of white pruinosity which begins a very short dis- 

 tance behind the anterior margin of the notum and extends two- 

 thirds of its length ; the posterior ends of the two bands blend into a 

 posterior patch of the same color, thus forming a white U ; very 

 narrow dark line running along midline ; humeral angles white- 

 pruinose ; perimeter of mesonotum and, at times, the entire mesono- 

 tum with numerous golden-yellow, appressed scales, these longer 



10 See footnote 6, p. 68. 



