20. DIPTERA OF NORTH AMERICA. [PART IV. 



Frotoplasa and Tanyderus, this cross-vein exists, and its position 

 is altogether as in the T. hrevipalpi. The rest of the venation 

 of the Ptycliox)terina is peculiar and distinguished by the absence 

 of the sixth longitudinal vein ; still this venation is more like 

 that of some T. hrevijMJpi, than of any T. UmgipaJpi; there is 

 hardly any vestige of a fold across the wing. The general appear- 

 ance and the coloring of the body and of the wings are much 

 more like the T. hrevipalpi ; the structure of the antennas and the 

 number of their joints also remind us of them. The elongated 

 epistoma, however, in Bittacomorpha and Ptyclioptera, shows 

 something of the nasus peculiar to the T. lovgipalpi ; it is not 

 apparent in Protop)Jasa. The PfycJiopterina keep . the wings 

 divaricate in repose (I do not know whether this applies equally 

 to Protoplaaa). 



In the Cylindrotomina, the course of the auxiliary and first 

 longitudinal veins strongly remind us of the T. longipalpji ; the T. 

 h7\^.vipalpi with a single submarginal cell, as far as known, never 

 have spurs at the tip of the tibia-, whereas the Cylindrotomina 

 partake of both of these characters at the same time ; the T. 

 brevipaljn with a single submarginal cell always have only four 

 posterior cells, Cylindrotoma distinctissima and G. americana 

 have a single submarginal cell and five posterior cells. At the 

 same time, the number of the antennal joints of the Qylindrotomina 

 (16), the position of the posterior intercalary vein and the struc- 

 ture of the palpi, are characters belonging to the T. hrevipalpi. 

 The Cylindrotomina, except in the above quoted instance, have 

 four posterior cells, a character of common occurrence among the 

 T. hrevipalpi, and, as fdr as I know, not observed yet among 

 the T. longipaljn. (Compare, for more detail, the chapter on the 

 Cylindrotomina. ) 



Thus, if we adopt the division into T. longipaljn and T. hrevi- 

 palpi, it will be necessary to form a third group which will be 

 artificial and contain the intermediate and anomalous forms.' 



1 It was with this intention that I introduced in the first volume of the 

 present series [Monographs, etc., Vol. I, p. 11) the group Ptijchopierina, co- 

 ordinate with the T. loncjipalpi and hrevipalpi (following Mr. Loew's prece- 

 dence, I then called them Tipuliiia and Limnohina). With the Cylindrotomina 

 I was hardly acquainted at that time, as I had found on this continent only 

 a single douhtful specimen. It may not be amiss to notice here, that the 

 two last lines of the above quoted page contain a lajisus calami, which 



