4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 79 



Female with the genitalia terminating in a thick fleshy tubular 



ovipositor. 



Legs rather slender; hind tibiae ciliate, usually with one longer 



bristle near middle; claws and pulvilli elongate in male, not in 



female. 

 Wings ordinary in shape ; fourth vein without stump at bend, the 



last section curved inward; hind cross vein joining fourth much 



nearer bend than small cross vein; last section of fifth vein very 

 short. First posterior cell open well before wing tip. Veins bare 

 except a few hairs at base of third. Costal spine vestigial or absent. 

 SpecifiG characters. — Our species separate into two groups in the 

 male sex on the presence or absence of abdominal patches of matted 

 hairs on the venter of the third or fourth tergites. I consider the 

 patches present only when they are limited by a sharp or well-defined 

 margin. Several species are intermediate in this respect, for exam- 

 ple, in deiIephilo£^ cecropiae^ and latevittata the venter of the third 

 and fourth abdominal segment at the center on either side is thickly 

 pilose, but the hairs gradually become thinner and shorter outward 

 from the middle and blend with the normal vestiture at the sides 

 without any definite break or margin circumscribing the dense hairs. 

 These and all similar forms are included in the series considered to 

 have the patches absent. 



The abdominal patches referred to are developed in a number of 

 different ways seemingly constant within the species and offer sev- 

 eral good characters of taxonomic value. Although the male geni- 

 talia are very similar in structure throughout the group, the shape 

 and comparative length of the inner and outer forceps are quite 

 distinctive for a number of species. The females offer even fewer 

 characters than the males, and except in rare cases they can not 

 always be separated with certainty or associated with the opposite 

 sex. The width of the front in relation to the total head width, 

 especially in the males where the greatest variations occur among 

 species, and the length of the third antennal joint compared Vvith 

 the second, furnish serviceable characters for classification, although 

 some variations must be anticipated. Thoracic chaetotaxy is quite 

 too uniform to give any specific characters aside from a few cases, 

 and I have omitted it almost entirely. Details of the frontal bristles 

 and of the pollen on the front, face, and abdomen furnish additional 

 points of some value in separating the species. The color pattern 

 of the abdomen varies within some species and must be viewed with 

 suspicion. The ciliation of the hind tibiae is developed in various 

 degrees but is subject to sexual variation in the species. In the 

 females the genitalia are identical in structure throughout consisting 

 of a fleshy protractile blunt-tipped ovipositor. 



