NO. I BLACK FLIES OF GUATEMALA DALMAT 139 



to the row of spines ; segment 8 with 16-30 simple spines in an unin- 

 terrupted row across the anterior margin and with numerous comb- 

 like groups lateral to each end of the row; segment 9 with 4-12 

 (usually 10) simple spines in a transverse row across anterior margin, 

 divided by median space, and with several comblike groups lateral to 

 the row. Ventral surface of abdominal segments: No granulosity; 

 all spines are anteriorly directed ; segment 4 with a single simple spine 

 on either side of midline ; segments 5-7 with 4 spines in transverse row 

 across posterior margin ; all spines on segment 5 are bifid ; on seg- 

 ments 6 and 7 the two outer spines are simple, the inner one bifid ; the 

 two spines on either side of the midline of segments 6 and 7 are more 

 separated than those on segment 5, the distance between them approxi- 

 mately equal to that of the median space. Terminal spines small, 

 flattened, conical, the apex sclerotized. 



Respiratory apparatus (pi, 36, fig. 286) of each side arising just 

 posterior to anterior margin of thorax ; composed of 8 filaments which 

 branch as follows : 3-3-2 ; filaments with superficial annulations and 

 with microscopic spicules. Maximum length of filaments, 2.5 mm., 

 about 0.7 times the length of the cocoon ; average diameter, 40 fi. 



Cocoon (pi. 39, fig. 326) : Length of base, 3.5 mm. ; maximum 

 width, 2.0 mm. ; maximum height, 1.6 mm. Cocoon wall-pocket type, 

 without collar ; texture of case parchmentlike, spongy, with threads 

 visible ; rim around anterior aperture thickened. Cocoon covering 

 abdomen and two-thirds of thorax ; attached along the posterior half 

 of its base. 



Larva (pi. 40, fig. 365, and pi. 42, fig. 402).— Total length, 5.3-5.5 

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

 1.6 times width of head. First 4 abdominal segments slightly wider 

 than head capsule ; segments 5-7 noticeably expanded, reaching the 

 greatest width at segment 6 which is 1.7 times the width of segment i ; 

 posterior segments tapered ; body with same general shape as that of 

 larvae in subgenus Simulium. General color tan to yellow, with a large 

 black patch on the ventrolateral areas of segments 6 and 7. 



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

 plate 40, figure 365. Each cephalic fan with 36-42 pectinate branches, 

 the hairs on these branches simple, interspersed at regular intervals 

 with stronger, longer hairs that are also simple. Mandible with two 

 flattened teeth on its inner margin, the teeth appearing to emerge from 

 the same base ; both teeth sharp-pointed, the distal one longer and 

 broader. Antenna 360 ju, long, 4-segmented, light brown, just passing 

 the basal stalk of cephalic fan ; segment 2 longer than segment i ; 

 segment i with longitudinal striations. Submentum with 9 triangular- 



