NO. I BLACK FLIES OF GUATEMALA — DALMAT 175 



granulosity ; on each side of midline of thorax are 6 trichomes, one 

 arborescent, three trifid, one bifid, and one simple. Dorsal surface of 

 abdominal segments : Segment i with granulosity on anterior and pos- 

 terior margins which seems to be composed of small triangular-shaped 

 spines, grouped as in combs but not contiguous to one another. Seg- 

 ment 2 with 6 anteriorly directed simple spines in a transverse row 

 about three-fourths the distance back from anterior margin, the row 

 being divided into two by a median space ; on either side of this row 

 there are 3 hairs ; entire surface covered with minute spines as on 

 segment i ; segments 3 and 4 with transverse rows, somewhat before 

 posterior margins, composed of 8 spines, each row also divided by 

 median space ; anterior fourth of segment 3 covered by small, straight 

 spines, formed in groups of twos and threes ; segment 4 with wide 

 band of similar spines, in groups of 2 to 6, extending from middle of 

 segment to row of heavier spines ; segments 5-9 with band of minute 

 straight spines along anterior margins, these in groups of 2 to 6. 

 Ventral surface of abdominal segments : Fifth segment with 4 anteri- 

 orly directed spines in transverse row across its middle, the spines 

 divided into two equal groups by a median space ; segments 6 and 7 

 with similar rows of spines, but the two spines on each side of median 

 space are more separated than on segment 5, so that the distance be- 

 tween them is approximately equal to that of median space. Terminal 

 spines absent. 



Respiratory apparatus (pi. 37, fig. 293) of each side arising some- 

 what posterior to anterior margin in region of humeral angles, com- 

 posed of ID tubular filaments arranged in groups of 4-4-2. Maximum 

 length of filaments, 1.2 mm., about 0.24 times as long as cocoon; 

 average diameter, 40 /x ; filaments smooth, without microscopic 

 spicules. 



Cocoon (pi. 39, fig. 333) : Length of base, 3.6 mm. ; greatest length, 

 5.0 mm.; greatest width, 1.9 mm.; height, 2.0 mm. Cocoon slipper- 

 shaped, with distinct collar and fine parchmentlike texture, threads 

 not visible ; lateral margins not extended to form "wings." No fes- 

 toons or prolongations from rim of anterior aperture, but with 2 or 3 

 ribbonlike markings near dorsal aperture which are woven into the 

 cocoon itself. Cocoon covering abdomen and posterior fourth of 

 thorax. 



Larva. — None available. 



The male of Simidiiim (D.) ardeni appears closest to S. (D.) 

 yepocapense Dalmat on the basis of the wide mesonotal bands of 

 white pruinosity. However, it can easily be distinguished from the 

 latter by the color of the hind femur, tibia, and basitarsus, and by the 



