112 DIPTERA OF NORTH AMERICA. [PART II. 



jointed arista has an apical or a subapical position. Hypopygium 

 imbedded, distinctly hairy ; its outer appendages have a lamelli- 

 form structure and are usually concealed. Feet rather short and 

 comparatively strong. The first joint of the hind tarsi without 

 bristles. Wings in comparison rather broad and very rounded at 

 the tip ; the small transverse vein in most of the species very far 

 distant from the margin of the wing ; the last segment of the 

 fourth longitudinal vein straight, parallel or almost parallel to the 

 third longitudinal vein. 



I have already expressed myself in detail (see Diaphorus) 

 about the difficulty attending the distinction of the genera Dia- 

 phorus and Chrysotus. I have pointed out that I consider the 

 smaller size, the less slender form, the comparatively smaller size 

 of the wings, the smaller length of the feet, the not elongated pul- 

 villi of the fore tarsi in the male and the absence of stronger bris- 

 tles on the posterior end of the hypopygium, as those characters, 

 which enable us to distinguish the species of Chrysotus from 

 Diaphorus. 



The range of the genus Chrysotus is known to be Europe, Asia, 

 Africa, and America. The name of the genus (from ^pixjwToj, 

 gilded) has reference to the gold-green color of many species. 



Mr. Say has described three North American species of Chry- 

 sotus ; hardly one of the three probably belongs to this genus, as 

 Mr. Say seems to have misunderstood its characters ; Chrysotus 

 nubilus may be a Medeterus, C. concinnarius is perhaps a Dia- 

 phorus, and C. abdominalis is probably a Chrysotimus. In the 

 next place Mr. Macquart has described a female as Chrysotus 

 viridifemora ; if face and front are covered with white dust, as it 

 seems to follow from his description, this character and the color 

 of the feet may perhaps help to recognize the species. Finally, 

 Mr. Walker has, in his usual careless manner, published a Chry- 

 sotus incertus, which probably will remain incertus forever; as he 

 1ms not even stated the sex of the specimen described, his descrip- 

 tion is of no use whatever. 



I know, thus far, twelve North American species of Chrysotus, 

 of which five are represented in both sexes, three only in the male, 

 and four in the female sex ; two of the latter offer but so little 

 peculiar characteristics, that I hesitate with their publication, 

 while the two others are striking enough to preclude the possi- 

 bility of a mistake. 



