XVI BULLETIN 31, UNITED STATES NATIONAL MUSEUM. 



MICRODONINI. 



Anterior cross-vein near the base of the discal cell, or near the middle, and 

 more or less oblique. Marginal cell open. Legs slender, third joint of the 

 antennw, at least, elongate, the first more or less so. iMrge, species. 



a. Face rouuded, pilose. 



6, First posterior ceil with a stump of a vein from the third longitudinal vein ; 



scntellum flattened, usually with two points Microdon. 



hh. First posterior vein without such a stump of a vein; scutellum without points. 



MlXOGASTER. 

 tM. Face produced down wai'ds, bare Chrysotoxum. 



This group as here distiuguished is artificial. Microdon is one of the 

 most peculiar genera in the family. The presence of a stumj) of a vein 

 in the first posterior cell is characteristic, reappearing in Ceria, and 

 occasionally in species allied to EristaVis. The presence of i)oints on 

 the scutellum reminds one of the Stratiomyidce, but the resemblance is 

 not great. This character was used by Wiedemann to found the genus 

 Ceratophya, but it is of slight importance, two such closely allied species 

 as M. globosus and M. fuscipennis differing in its presence. Mixogaster 

 doubtless finds a place here, notwithstanding its club-shaped abdomen, 

 by reason of the structure of the head and wings. The European 

 Psarus likewise evidently finds its nearest relationship here, though 

 showing an affinity with Paragus of the next group. 



Chrysotoxum is more aberrant, and is a disturbing element in the 

 arrangement of the genera. The only thing it has in common with 

 Microdon is the elongate antennae ; the neuration approaches more that 

 of the second division. Singularly, too, the genus is a close one, the 

 species all showing great structural and color resemblance. Why the 

 group Chrysotoxinw should be retained to embrace forms so diverse as 

 Orthoneura and Pipiza I do not understand. 



CHII.OSINT. 



Small to moderately large species, seldom with light markings (Paragus 

 Chilosia, Pipiza spp.), usually the color is uniformly dark, with or with- 

 out metallic greenish markings, or tcholly deep Mack, the face never yellow 

 {except in Paragus), the abdomen never with entire cross-bands. Third 

 longitudinal vein nearly straight, anterior cross-vein basal discal. 



a. Epistonia protuberant, antenna'- often elongate, outer cross-veins more or less in- 

 flected. 



b. All the femora thickened and with a row of short spines below; body clothed 



with K]>arHe tomentum Lepromyia Will. 



bb. Femora not thickened ; body not tonientose. 



c. Front in feinale, and face in both sexes often, with transverse wrinkles; false 



vein of wing usually obsolete Chrysogaster Meig. 



CO. Front and face not with wrinkles; face hairy, concave Psilota Meig. 



aa. Epistonia not projecting, or, if so, the hind femora thickened; outer cross-veins 



more usually reflected, antenuai usually short. 



