OSTEN SACKEN ON WESTERN DIPTERA. 317 



POLYMEDON 110 V. geil. 



Face of the male prolonged downward, and dependent in the shape 

 of a silvery sheet, or ribbon ; in length, this ribbon is about equal to the 

 upper part of the face between the auteunas and the lower end of the 

 eye. In life, the ribbon is straight; iii dried specimens, its end is usually 

 bent inward. 



Cilia of the very small tegulfB in the male unusually long (bent back- 

 ward, they would almost reach the end of the second abdominal seg- 

 ment); they can be- folded together like a fan, and then form a long 

 tapering horn- or spine-like body. Those specimens which I examined 

 in life had the cilia folded in that way; in the dried specimens, they are 

 sometimes spread out. 



These two extraordinary characters define the genus sufficiently ; the 

 other parts of the body may be described as follows: — 



Antennae comparatively short; first joint with a few hairs above; 

 second small; third suboval, with a blunt end; arista subapical, of 

 moderate length and stoutness (the antennse resemble figure 10, d, on 

 plate iv, of volume ii, of the Monographs, etc.). 



Face of moderate breadth, nearly parallel, prolonged in the male, as 

 described above; in the female, the face has the usual structure; its 

 lower edge is nearly on a level with the lower corner of the eye, and is 

 not straight, but somewhat angular (compare 1. c, tab. iii, f. 6, 6, where,, 

 however, the face is much uarrow^er). 



The usual frontal pair of diverging bristles is present; the other con- 

 verging pair, insei'ted at the upper corners of the eyes, is so minute as 

 to be almost imperceptible in the male; it has the usual size in the 

 female. 



Thorax. — In the male, the double row of minute bristles, usually pres- 

 ent in the middle of the dorsum, is altogether wanting; it exists in the- 

 female; the lateral rows of larger bristles are present in both sexes. 



Hijpopygium comparatively large and stout, nearly sessile ; external 

 appendages lamelliform, rather small, fringed with bristles. 



Legs of moderate length ; first joint of the hind tarsi without bristles. 



Wings. — The last section of the fourth vein turns off before the mid- 

 dle, and converges toward the third in a very gentle curve; fifth vein in 

 the male obsolete before reaching the margin ; in the female, very much 

 attenuate. Costa ( 5 ) so much swollen before the tip of the first vein 

 as to fill out the whole costal cell, except small spaces at both ends ; in 

 the female, the swelling is hardly perceptible. 



Polymedon is a mythological name. 



PoLYMEDON FLABELLiFER n. sp. — Face and front silvery-white in 

 the male, as well as the dependent ribbon; greenish-white in the fe- 

 male; cilia of the inferior orbit w^hite; palpi black; antennne brown 

 above, yellowish-red on the under side. The dark metallic-green thorax 

 in the male is almost altogether covered with a very striking silvery 

 bloom, especially on the dorsum ; in the female, this bloom exists only on 



