I. FAMILY 



Helobia hybrida, enlarged. After Washburn. 



Large to moderately small, slender flies, with long, 

 slender legs. Head subspherical ; occiput strongly de- 

 veloped; face often produced snout-like. Eyes round, 

 separated by the broad front; sometimes approximated 

 above and below the antennae, but never contiguous. 

 Ocelli almost always ( Ti ichocera) wanting. Antennae 

 rarely shorter, usually longer than the head and thorax 

 together; bead or thread-like, composed of from six 

 ( Amsomera) to thirty-nine ( Cerozodia* ) joints, the joints 

 of the flagellum never plumose, but usually with more 

 or less conspicuous bristly hairs; the joints sometimes 

 serrated or pectinated; usually there are eleven, twelve 

 or fourteen joints in the flagellum. Proboscis more or 

 less projecting, in a few genera very much elongated; 

 palpi four or five jointed, the terminal joint often elon- 



' This genus, from Australia, has, according to Osten Sack en, from 

 twenty-nine to thirty-seven joints in the flagellum, all of which, ex- 

 cept the terminal one or ones, are branched. 



(10) Si 



