12 D1PTERA OF NORTH AMERICA. 



removed from it towards the base of the wings ; palpi in most 

 cases short ; last joint either very short, or, if elongated, hardly 

 longer than the three preceding taken together LIMNOBINA. 



III. Sixth longitudinal vein (anal vein of the former authors) obsolete. 



PTYCHOPTEKINA. 



The two first large groups are further distinguished by the structure of 

 the genital organs of the male, which, in most of the Limnobina, are 

 represented by a forceps, consisting of two movable, fleshy lobes, with 

 some delicate horny appendages ; whereas in the Tipulina the forceps is 

 a very compound organ, consisting of manifold horny pieces, which, being 

 inclosed between the dorsal and ventral plates of the two last abdominal 

 segments, produce the club-shaped appearance peculiar to the tip of the 

 $ abdomen of this sub-family. 



Thus founded, not on a single character, but on a combination of cha- 

 racters taken from various organs, the definition of the two great sub- 

 families hardly leaves any doubtful case among the Tipulidas which I 

 know of. If one character fails to give a satisfactory result, the others 

 will generally remove at once any doubt as to the relationship of the spe- 

 cies. Thus, the last joint of the palpi of Pedicia is unusually long ; but 

 the auxiliary vein, ending in the subcosta, and the presence of a cross 

 vein between it and the second vein, immediately refer it to the Limnobina, 

 where this genus naturally belongs on account of its habitus. (I have 

 neglected to examine this last joint in fresh specimens of Pedicia, but it 

 appears very probable that its disproportion with the other joints is far 

 from being so striking as is the case in the' Tipulina.') 



In Rhamphidia, the last joint of the palpi is represented by former 

 writers to be elongated. I had no occasion to ascertain, on living speci- 

 mens, how far this is correct. But the presence of the cross vein places 

 this genus among the Limnobina, where it naturally belongs by its habitus. 

 And even if this character should not be considered as sufficient, on account 

 of the extreme shortness of the cross vein, placed at the very tip of the 

 auxiliary vein, the structure of the male genitals removes all doubt. 



In some Pachyrhinae there is, near the tip of the auxiliary vein, a blackish 

 dot, which might perhaps be mistaken for a cross vein. But should it 

 even be considered as a rudiment of one, the length of the last joint of 

 the palpi, the structure of the male genitals, etc., assign its place among 

 the Tipulina, where its habitus most evidently refers it. 



In the singular genus Antocha 0. S. the costa and the auxiliary and the 

 first longitudinal veins coalesce insensibly together, so that there is no 

 room left for a cross vein. In this case, the shortness of the palpi and 

 the structure of the male genitals decide of its location among the Lim- 

 nobina. 



I refer to my sub-family of Plychopterina the genera Ply chapter a, Bittaco- 

 morpha, and Protoplasa (with its congener Macrochile Loew). As to the 

 distribution of the other genera among the two remaining sub-families, I 

 agree with Mr. Loew, with the following exceptions : 



