NO. I BLACK FLIES OF GUATEMALA — DALMAT 203 



Respiratory apparatus (pi. 37, fig. 299) of each side arising behind 

 the humeral angles of the thorax, each composed of 18 filaments which 

 branch as follows : 6-2-8-2 ; filaments with superficial annulation and 

 with microscopic spicules; filaments extended so that they appear to 

 form an open fan. Maximum length of filaments, 2.6 mm., about 0.4 

 times the length of the cocoon ; average diameter, 28 ju,. 



Cocoon (pi. 39, fig. 339) : Length of base, 4.9 mm. ; maximum 

 length, 6.6 mm. ; maximum width, 3.2 mm. ; maximum height, 3.0 mm. 

 Cocoon slipper-shaped, with distinct collar and fine parchmentlike 

 texture, threads not visible ; no festoons or prolongations ; rim around 

 anterior aperture thickened. Cocoon covering abdomen and half of 

 thorax. 



Larva (pi. 41, fig. 377, and pi. 42, fig. 414). — Total length, 11.6- 

 12.7 mm. Length of head i.i times its width. Width of thorax 1.6 

 times width of head. Abdominal segments 1-4 about equal in width 

 to thorax; segments 5-7 about 1.3 times width of segments 1-4; ex- 

 pansion of abdomen is gradual from anterior to posterior ends, seg- 

 ment 8 narrowing rapidly ; in profile, larva appears like others of 

 subgenus Dyarella. General color yellow to gray, with no dark patches 

 on ventrolateral regions of segments G-y. 



Head: Frons-clypeus usually all dark, although at times a more 

 distinct pattern is visible ; designs on frons-clypeus and epicranial 

 plates shown on plate 41, figure 377. Each cephalic fan with 51-52 

 pectinate branches, the short hairs on these branches simple, close 

 together, interspersed with stouter, slightly longer hairs at regular 

 intervals. Mandible with only i well-developed tooth on its inner 

 margin, an indication of a second minute tooth visible somewhat closer 

 to the base. Antenna 430 ju, long, light yellow in part, dark brown on 

 remainder, 4-segmented, just passing the basal stalk of the cephalic 

 fan; segment 2>i>3 ; segment i with small white patch at its base, 

 the rest dark brown ; segment 2 almost transparent except for 2 

 dark-brown patches beyond the middle, and i longitudinal patch ex- 

 tending from the base to first of 2 patches near midregion ; segments 

 3 and 4 dark brown, appearing almost black; segment i with longi- 

 tudinal striations. Submentum with 11 apical teeth, the middle seven 

 of approximately the same length, like one end of a hexagon in shape ; 

 two outer teeth on either side are light yellowish in color, smaller than 

 the others ; ventrolateral row composed of 1 1 hairs in straight line, at 

 least the apical six hairs bifid; lateral margin of submentum with 9 

 very small toothlike indentations near the apex. Occipital cleft 

 pointed, deep, and broad (pi. 42, fig. 414). 



Thorax and Abdomen : Pseudopod (thoracic proleg) with 65-70 



