WYEOMYIA CCENONUS 153 



Chagres River, Canal Zone, March 18, 1909, " from tree-hole in bush back of 

 station on trail to Vigia " (A. H. Jennings). 



This species is peculiar from its marked sexual dimorphism and the very long 

 air-tubes of the pupa. The differences between the sexes led to their being 

 described as distinct species, our types of circumcincta being all males, the 

 macrotus all females. Subsequently an excellent series of both sexes was re- 

 ceived from Mr. Jennings and was determined as a new species and described 

 under the name andropus, as certain errors in the association of subsequent 

 specimens and in the preliminary tables before us led us to this course. We had 

 placed Avith macrotus some males with dark tarsi which resembled it, while the 

 circumcincta had been classified under the heading " eyes with a white margin." 

 In strongly marked males there is a faint trace of this marking, but we consider 

 it too slight to be described as present. Our final study led to the correction of 

 these errors and the recognition of the above synonymy. 



WYEOMYIA CCENONUS, new species. 



Description of Female and Male of Wyeomyia ccenonus (Larva Unknown) : 



Female. Proboscis rather short, swollen apically, vestiture black with a 

 bronzy and blue reflection; labellge small^ rounded, with fine outstanding setae. 

 Palpi short, flattened, one-sixth as long as proboscis, bronzy black. Antennae 

 moderate, the joints slender, subequal, rugose, coarsely pilose, black ; tori sub- 

 spherical, with a cup-shaped apical excavation, blackish, with a slight prui- 

 nosity ; hairs of the whorls long, rather sparse, black. Clypeus rounded, convex, 

 blackish pruinose. Eyes separated at the vertex by a narrow wedge, bluish black. 

 Occiput clothed vnih flat dark-brown scales with a slight metallic reflection, a 

 white patch at sides below ; two long hairs at the vertex and smaller ones along 

 margin of eyes. 



Prothoracic lobes large, elliptical, well separated, clothed with flat scales, 

 dark brown like mesonotum, with dark-blue reflection, a row of setae on anterior 

 margin. Mesonotum clothed with elliptical, flat dark-brown scales with sub- 

 metallic reflection, scales on lateral angles whitish ; bristles over roots of wings 

 dark brown. Scutellum trilobate, with vestiture similar to and continuous with 

 that of mesonotum, each lobe with a small tuft of dark-brown bristles. Post- 

 notum elliptical, prominent, brown, a group of setae near posterior margin. 

 Pleurae and coxaB luteous, clothed with elliptical, flat silvery- white scales. 



Abdomen subcylindrical, compressed, truncate apically and with many brown 

 terminal setee ; dorsal vestiture black, with a slight bronzy and blue reflection ; 

 venter silvery white, the colors separated on the sides in a straight line. 



Wings moderate, hyaline; petiole of second marginal cell one-third as long 

 as its cell, that of second posterior cell shorter than its cell ; basal cross-vein 

 distant less than its own length from anterior cross-vein ; scales of veins broadly 

 ovate, obliquely subtruncate at tips, black, with a blue and bronzy reflection on 

 costa. Halteres pale with blackish knobs. 



Legs rather long and slender, black with bronzy and blue reflection, the 

 femora whitish beneath at base; tibiae and tarsi with a paler luster beneath. 

 Claw formula, 0.0-0.0-0.0. 



Length : Body about 3 mm. ; wing 3.5 mm. 



Male. Proboscis as in the female. Palpi very small. Antenna similar to 

 those of the female, the hairs of the whorls longer and more abundant, a small 

 secondary subapical whorl on each joint. Coloration of head and body as in the 

 female. Abdomen rather slender, considerably expanded toward tip, the 

 claspers long and prominent, widely separated. Wing slightly narrower than 

 in the female, vestiture somewhat sparser. Mid legs yellowish silvery beneath, 

 broadened on last four tarsal joints. Claws on mid tarsi large, unequal, the 



