86 NEW YORK STATE MUSEUM 



The wings are usually rather slender and delicate, with the 

 anterior veins (those, nearest the costal border) rather stout, 

 while the posterior veins are usually very delicate and indistinct. 

 The surface of the wing is delicately hairy in a number of species, 

 though the majority have bare wings. 



Below is given the Comstock-Needham terminology of wing 

 venation as used in this paper, together with the equivalent terms 

 of the 'Schinerian system as applied with but slight modifications 

 to the Nematocera generally : 



Comstock Needham Schinerian 



Costa (O) = Costa 

 Subcosta (Sc) = Auxiliary 

 Radius (R 1 ) = First longitudinal 

 R^ = Second " 

 R 4+5 = Third 

 Media (M) = Fourth 

 Cubitus (Cu) Fifth " 



Anal (A) = Sixth 



The costa ends at or before the tip of the wing in all the 

 genera; the subcosta, though sometimes rather indistinct, is 

 usually present; the radius is stout and well developed, and 

 usually with two or three branches, R 2 in some genera appear- 

 ing like a crossvein ; the media usually present and always sim- 

 ple; the cubitus is nearly always two-branched; anal vein usually 

 present though delicate. Compare pl.17, figs.13-16, pls.27 to 31. 

 The halteres, the slender organs with knobbed ends which are 

 supposed to be the rudimentary second pair of wings, are rarely 

 wanting. 



For a description of the internal anatomy of both larva and 

 imago the reader is referred to Miall and Hammond's work on 

 the harlequin fly (1900). 



A large number .of genera have been erected to contain the 

 species of the world. Of these some may be placed as the 

 synonyms of others, leaving still over 40 valid genera. In order 

 to facilitate identification a key to the North American genera- 

 is offered besides the more general one for the genera of the 

 world. 



