224 DIPTERA OP NORTH AMERICA. [PART II. 



American species is known, which may perhaps be identical with 

 one of the European species. 



1. X. lielvinus LOEW. " J. Flavus, fronte, facie et setis thoracis 

 nigricantibus. 



Yellow, front, face and the bristles of the thorax blackish. Long. corp. 

 0.11. Long. al. 0.13. 



STN. Xanthochlorus helvinus LOEW, Neue Beitr. VII, 75, 1. 



Altogether yellow. Front and face blackish with whitish dust, 

 which is more distinctly visible in an oblique direction. The 

 arista, the bristles on the vertex and on the upper side of the 

 thorax, black, but shifting into brown in a reflected light. A 

 small blackish spot on the pleurae, immediately below the root of 

 the wing. 



Hob. Chicago. 



Observation. This species resembles the European X. tenellus 

 Wied., very much, and is probably a slight variety of it. No 

 plastic distinctions at all are to be seen ; the only difference which 

 I can perceive, is the darker color of the bristles upon the vertex 

 and on the upper side of the thorax. The comparison of the male 

 is necessary in order to determine whether this species can be con- 

 sidered as a variety of X. tenellus. 



Gen. XLII. SAUCROPUS. 



The species of this genus, which older authors have united with 

 Porphyrops, agree in many characters so much, and differ by 

 these characters so sharply from the related species of the Doli- 

 chopodidse, that their claim to form a separate genus cannot be 

 questioned. The following are the principal characters of this 

 genus : First joint of the antennae without hair on the upper side ; 

 arista dorsal. The thorax with a sloping area upon the mid- 

 dle of its posterior end. Feet very long and slender ; hind tibia? 

 elongated ; the first joint of the hind tarsi without bristles, shorter 

 than the second. Abdomen elongated and narrow ; especially in 

 the male. Hypopygium disengaged, short and stout, inflected, 

 with short, very little developed appendages. Color of the body 

 principally, or at least partially, yellow. Hairs and bristles 

 chiefly black. 



