NO. I BLACK FLIES OF GUATEMALA — DALMAT 229 



Larva (pi. 41. fig. 383, and pi, 43, fig. 420). — Total length, 4.4- 

 5,0 mm. Length of head capsule 1.2 times its width. Width of thorax 

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

 of head ; segments 5-7 expanded, with greatest width (segment 6) 1.7 

 times width of segment 1-4 ; body with same general shape as that of 

 metallinim. General color greenish yellow ; a wide dark-green to gray 

 band almost completely encircling the thorax along its anterior margin ; 

 large gray patch just posterior to pseudopod ; dorsum of segments 5-8 

 darker than remainder of abdomen ; segments 6 and 7 with dark 

 patches on the ventrolateral regions. 



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

 plate 41, figure 383. Each cephalic fan with 28-34 pectinate branches, 

 the hairs on these branches all appearing to be of one type, rather 

 heavy, long, and close together. Mandible with 2 teeth on its inner 

 margin, the teeth appearing to have a common base, the division be- 

 tween them rather deep ; both teeth sharp-pointed, the distal one about 

 twice the length of the other. Antenna 310 /* long, 4-segmented, pale 

 yellow, surpassing the basal stalk of the cephalic fan ; segments i and 

 2 subequal, each slightly shorter than segment 3 ; segment i with 

 marginal indentation near the middle ; segment 2 appears to be super- 

 ficially divided into 2 segments one-third the distance from its base ; 

 no transverse striations. Submentum with 9 apical teeth, rather 

 slender and blunt, somewhat separated, none of the teeth much longer 

 than the others ; ventrolateral row with 4-5 hairs in straight line, all 

 simple ; lateral margin of submentum with about 5 toothlike indenta- 

 tions. Occipital cleft extremely deep, reaching the base of the sub- 

 mentum, strongly convergent toward the middle of the lateral margins 

 (pi. 43, fig. 420). 



Thorax and Abdomen : Pseudopod (thoracic proleg) with 34 

 rows of hooks on its apex ; postclypeal sclerites usually not present, at 

 times just visible. Posterior sucker with 74-76 rows of hooks. Anal 

 gills with 3 main divisions each with 8 fingerlike extensions of ap- 

 proximately equal length. Anterior and posterior arms of X-shaped 

 sclerite well sclerotized ; triangular-shaped patch over each anterior 

 arm, the apex of patch at anterior extremity, gradually widening pos- 

 teriorly, the patches of both arms fusing at the midline; bases of 

 patches contiguous with posterior arms ; posterior arms extending to 

 lateral margins of larva ; no rectal scales. Eighth segment with 2 ven- 

 tral papillae which are small and transparent, the apices rather 

 pointed ; no sclerotized plaques. 



Types. — $, lost ; type locality given as "Mexico." There are Mexi- 

 can specimens of this species in the British Museum. 



