DIPTEKA. 233 



CHRYSOCHROMA. 



Chrysonotus, Loew, Verh. zool.-bot. Ges. Wien, 1855, p. 146 (nomen prseocc). 

 Chrysochroma, Williston, Manual North- American Dipt. p. 47 (1896). 



The genus Chrysonotus was separated from Sargus by Loew to include species in 

 which the ocelli are equidistant, the colouring metallic, the hind femora not thickened, 

 and the arista not thickened at the base. In Merosargus he placed lighter-coloured 

 forms, with the hind femora thickened and the arista thickened on its proximal portion. 

 These characters united are not tenable when applied to the American species. I have 

 in the following pages placed the metallic forms with this genus and the non-metallic 

 species with Merosargus. In all of them the eyes of the males are separated. Merosargus 

 also closely approaches Ptecticus, though it is sometimes difficult to say whether the 

 second antennal joint is prolonged on the inside or not. I thought at one time that the 

 position of the point of origin of the second vein would serve to distinguish Merosargus 

 from Chrysochroma, but I have not as much faith now in the character as formerly. 



3 . Chrysochroma pulchrum, sp. n. 



§ . Front yellow in the middle, on the sides grooved and black ; on the lower portion light yellow, moderately 

 elevated and nearly square in shape. First joint of the antennae black, second and third reddish-yellow ; 

 arista moderately thickened at the base. Face and proboscis light yellow, the oral margin very narrowly 

 in front and the narrow cheeks black. Mesonotum finely serobiculate, moderately shining, deep blue, 

 with violaceous reflections ; pile golden-yellow, short. Scutellum coloured and sculptured like the 

 mesonotum. Pleurae deep blue, with white pubescence ; a spot below the dorso-pleural suture shining 

 metallic green or blue. Abdomen deep indigo-blue, not shining, with slight violaceous reflections ; the 

 posterior part of the third segment, the larger part of the fourth segment, and the whole of the fifth 

 segment covered with golden-yellow pile. Legs light yellow, including the front coxae ; distal half or 

 more of all the femora and the two distal joints of each tarsus black. Wings lightly infuscated ; the 

 furcation of the second and third veins takes place a little beyond the junction of the anterior cross-vein. 

 Length 6-9 millim. 



Hab. Mexico, Chilpancingo and Amula in Guerrero (H. H. Smith). 

 Two specimens. 



2. Chrysochroma flavopilosum. 



Chrysonotus flavopilosus, Bigot, Ann. Soc. Ent. Fr. 1879, p. 227 l . 



Hab. Mexico 1 , Amula, Chilpancingo, Xucumanatlan, and Omilteme in Guerrero, 

 Cuernavaca in Morelos (H. H. Smith), Tepic {Schumann). 



Two females and thirteen males. I was first inclined to identify this species, not 

 recognized by Osten Sacken (antea, p. 42), with Chrysonotus ceneiventris, Giglio-Tos, 

 and I am not sure but that the latter name is a synonym. The material is such as to 

 warrant a full description of the species : — 



cJ . Front narrow, about as wide as the length of the second and third joints of the antennae together; shining 

 green, on the lower part white. Antennae red, the first two joints brown. Face shining black, with long 



biol. cente.-amee., Dipt., December 1900. 2 h 



