134 DIPTERA OF NORTH AMERICA. [PAHT II. 



Dolichapodidse carefully, nevertheless its observation is important, 

 as it is of very great service for the specific distinction as well as 

 for the generic location of such females of different species which 

 resemble each other very closely. 



The name of the genus (from awroppou, I connect by inserted 

 pins) has reference to the characteristic formation of the second 

 joint of the antennae. 



As yet only European species of Syntormon have become 

 known. 



Gen. XVI. SIX AUTIIIU S. 



The following are the most important characters of this genns : 

 The first joint of the antennae without hairs ; the second reaching 

 more or less on the inner side of the third, usually forming in the 

 males a thumb-like projection, and in the females a more rounded 

 lobe ; the third joint of the antenna? in the males elongated and 

 pointed ; arista apical or so near the extreme tip of the antennae, 

 as to be taken for such. Scutellum usually bare, first joint of the 

 hind tarsi without bristles. The hypopygium small, imbedded, 

 with very small, often not distinctly perceptible appendages. 



That Synarthrus differs from Syntormon only by the absence 

 of hair upon the first joint of the antenna?, has already been stated. 



Of the three species described below, two undoubtedly belong 

 to the genus Synarthrus. This cannot be said with regard to 

 the third species, Synarthrus barbatus. Its position in the genus 

 Synarthrus can only be a temporary one, brought about by the 

 difficulties of placing it into another genus. It is sufficiently dis- 

 tinguished from the other species of Synarthrus by the peculiarity 

 alone, that the second joint of the antennae encroaches only very 

 little on the inner side of the third. In its general appearance it 

 approaches the species of Porphyrops very closely, so that I leave 

 it undecided whether it would not be better located there. The 

 size of the pulvilli of the fore tarsi betrays a relationship with 

 Eutarsus and Diaphorus, the structure of the antennae, however, 

 does not allow its location in these two genera. To erect a new 

 genus does not seem advisable, as the species shows close rela- 

 tionship in various directions. 



The name Synarthrus (from avv, together, and dp^pov, joint) 

 has reference to the peculiar mode of connection between the 

 second and the third joints of the antennae. 



