38 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



1. Middle tarsi of male modified palmaris Loew. 



Middle tarsi of male plain 2 



2. Fore coxae entirely yellow cinereiventris Loew. 



Fore coxae only tipped with yellow 3 



3. Front metallic violet affinis, sp. nov. 



Front dull metallic green stratcsgus, sp. nov. 



38. Synarthrus cinereiventris Loew. 



Plate III, Figs. 62 and 63. 



This species appears to be very rare in the Middle 

 States, the male from which I described this sex' being 

 the only specimen I have ever found. It is easily distin- 

 guished from the males of the other species in having a 

 close-set graduated series of six robust black bristles on the 

 lower surface of the proximal half of the middle femur. 

 The posterior cross-vein in this species is about the same 

 length as the distal segment of the fifth vein. 



39. Synarthrus affinis, sp. nov. 



Plate III, Figs. 56-59. 



Male. 3.5-4 mm.; length of wing 2.5-3 Tm^- Palpi very small, white. 

 Face narrow below, covered with silvery white dust, more gray towards the 

 antennee. Antennae black, basal joint with a few distinct hairs on its mesial 

 surface, terminating in a prominent ventral projection; overlapping portion 

 of second joint thumb-shaped; third joint as long as the face, completely 

 covered with short but distinct pile, rapidly tapering, its ventral more con- 

 vex than its dorsal contour; arista very nearly apical, as long as the third 

 joint, pubescent. Front shining metallic violet. Postocular cilia of moderate 

 length, white. Thorax metallic golden green, somewhat dimmed with pale 

 dust, especially in front. Scutellum metallic bluish green. In some speci- 

 mens the abdomen is metallic golden green, the basal portion of each seg- 

 ment more cupreous, in others the abdomen is cupreous and the bases of the 

 segments are dark. Hypopygium almost completely concealed. Pleurae 

 dark metallic green, covered with white dust. Coxae black, turning yellow 

 towards their tips, covered with pale hairs. Legs yellow, tarsi infuscated or 

 blackened from the tip of the first joint; hind femora with a broad black 

 band near the tip; tip of hind tibia distinctly blackened; hind metatarsus 

 with a peculiar recurrent sickle-shaped black bristle on its plantar surface; 

 middle femur with an even series of black bristles along its lower surface 



1 Psyche, Vol. V, i8go, p. 362. 



