NO. I BLACK FLIES OF GUATEMALA — DALMAT 217 



close together ; rim around anterior aperture not thickened. Cocoon 

 covers the abdomen and thorax ; attached along posterior half of its 

 base. 



Larva (pi, 41, fig. 380, and pi. 43, fig. 417). — Total length, 5.9- 

 6.1 mm. Length of head capsule i.i times its width. Width of thorax 

 1.4 times that of head. First 4 abdominal segments 1.2 times width of 

 head ; abdominal segments 5-7 expanded, greatest at segment 6 which 

 is 1.6 times abdominal segments 1-4 ; cross section and profile like that 

 of metallicum. General color tan to gray, with dark-brown patches 

 on ventrolateral areas of segments 6 and 7 ; light-gray collar across 

 the anterior margin of thorax, extending ventrally to the thoracic 

 proleg. 



Head: Designs on frons-clypeus and epicranial plates shown on 

 plate 41, figure 380. Each cephalic fan with 28 pectinate branches, the 

 hairs on these branches rather heavy, short, simple, and well separated, 

 not interspersed with other types of hairs. Mandible with 2 teeth 

 along its inner margin, the distal tooth well developed and somewhat 

 pointed, the other appearing like a protuberance from the base of 

 the distal tooth. Antenna 550 ju, long, 4-segmented, brown, the first 

 two segments alone surpassing the basal stalk of cephalic fan; seg- 

 ments I and 2 equal in length, each longer than segment 3 ; segments 

 I and 2 with transverse striations. Submentum with 9 apical spines, 

 each appearing like a half of a hexagon, the central tooth and the 

 outermost tooth on either side larger than the others ; ventrolateral 

 row composed of 4-6 hairs, at least the distal two bifid ; lateral margin 

 of submentum with 7 toothlike structures, the apical three heavily 

 sclerotized. Occipital cleft small, triangular in shape (pi. 43, fig. 417). 



Thorax and Abdomen : Pseudopod (thoracic proleg) with 20-32 

 rows of hooks on its apex ; postclypeal sclerites small but well sclero- 

 tized. Posterior sucker with 82-84 rows of hooks. Anal gills with 3 

 main divisions, each with 5 fingerlike projections that arise close to 

 one another, their ends somewhat pointed, all of almost equal length. 

 Anterior arms of X-shaped sclerite completely covered by wedge- 

 shaped patches ; posterior arms short, barely reaching the lateral mar- 

 gins of the larva ; dark patch visible between the two anterior arms ; 

 3 rows of rectal scales, each scale with 3 to 4 teeth at its apex; on 

 either side of dark central patch, and lateral to the anterior arms, is a 

 protuberance which is directed somewhat toward the midline, clothed 

 with long scales each of which has several teeth at its apex. Two 

 distinct ventral papillae on eighth segment, not very long, each some- 

 what double-lobed ; about 18-20 heavily sclerotized plaques in trans- 

 verse row between the papillae and posterior sucker, the more-lateral 

 plaques being somewhat larger. 



