NO. I BLACK FLIES OF GUATEMALA — DALMAT II5 



spine on either end of the row are 2 other spines, the more posterior 

 one very fine, the other one similar to the spines in the transverse row ; 

 segments 3 and 4 each with 8 simple spines in a transverse row some- 

 what before the posterior margin, with median separation. Other 

 segments devoid of spines. Ventral surface of abdominal segments : 

 All spines are anteriorly directed; segment 5 with 4 bifid spines in 

 transverse row in front of the posterior margin, with median separa- 

 tion ; segments 6 and 7 each with 4 spines in transverse row, with 

 median separation, the two spines on either side of the midline more 

 separated from each other than those on segment 5 ; the outer spines 

 simple, the inner spines bifid. Terminal spines very small. 



Respiratory apparatus (pi. 36, fig. 281) of each side arising a little 

 behind the anterior margin of the thorax; composed of 6 filaments 

 which branch at the same level as follows : 2-2-2 ; the respiratory 

 apparatus not uncommonly has 8 filaments, such pupae usually being 

 found in the streams from which dichoptic males are reared ; filaments 

 with superficial annulation and with microscopic spicules. Maximum 

 length, 2.4 mm., slightly longer than the length of the cocoon ; average 

 diameter, 24 (i. 



Cocoon (pi. 39, fig. 321): Length of base, 2.3 mm.; maximum 

 width, 1.2 mm.; maximum height, 1.2 mm. Cocoon of wall-pocket 

 type, without collar ; texture of case parchmentlike, without visible 

 threads ; rim around anterior aperture slightly thickened. Cocoon 

 covers abdomen and three- fourths of thorax; attached along the 

 posterior half of its base. 



Larva (pi. 40, fig. 361, and pi. 42, fig. 398). — Total length, 4.2-4.6 

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

 1.6 times that of head. First 4 abdominal segments i.i times the width 

 of head; segments 5-7 expanded, greatest at segment 6 which is 1.7 

 times the width of segments 1-4; abdomen almost round in cross sec- 

 tion ; body with same general shape as larvae of the subgenus Simu- 

 lium. General color brown gray; abdominal segments 1-4 with gray 

 ring completely encircling them ; eighth segment milky white, with no 

 markings except that formed by the patch of rectal scales ; ventro- 

 lateral dark patches at times present on segments 5-7. 



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

 plate 40, figure 361. Each cephalic fan with 27-33 nonpectinate 

 branches. Mandible with 2 very close teeth on its inner margin, the 

 distal one at least three times the length of the basal one ; the basal 

 tooth very minute and fine, almost like a spine. Antenna 250 fi long, 

 4-segmented, pale yellow, far surpassing the basal stalk of the cephalic 

 fan ; segments i and 2 so closely united that they almost appear as a 



