ANISOMERA. 241 



site the inner end of the second submarginal cell (a little anterior 

 to it) ; the subcostal cross-vein is very near its tip ; the tip of 

 the first longitudinal vein is nearly opposite the tip of the 

 posterior branch of the fourth longitudinal vein ; the marginal 

 cross-vein is a very short distance anterior to this tip ; the second 

 longitudinal vein originates about the middle of the length of 

 the wing, or a little before it (in the female) ; prsefurca long, 

 almost equal in length to the second submarginal cell, or some- 

 what longer (in the female) ; its course is straight ; the fork of 

 the second vein is very short, as in Goniomyia, and hence, the 

 first submarginal cell is triangular ; the petiole of this cell is 

 many times longer than the cell, and has the marginal cross-vein 

 about its middle ; the second submarginal cell, which is some- 

 what arcuated in shape, is longer than the first posterior ; the 

 inner ends of the three posterior cells are often nearly in a line ; 

 sometimes, however, the inner end of the second posterior cell 

 projects inside of this line ; the fourth vein is in a straight line 

 with its posterior branch ; the anterior branch (inclosing the 

 second posterior cell) is angular at the inner end ; as neitlier of 

 the branches is forked, there can be only three posterior cells and 

 no discal cell ; the three last longitudinal veins are nearly 

 straight. The European species have, in the main, an exactly 

 similar venation (compare the figures in Meigen, Vol. I, Tab. 

 VII, and Walker, Ins. Brit. Dipt. Tab. XXVI, fig. 9). The 

 species diifer, however, in one point only : the length of the first 

 submarginal cell ; in some species, this cell is longer than its 

 petiole, and in such cases the marginal cross-vein connects the 

 first longitudinal vein with the anterior branch of the second, 

 and not with the petiole. It seems that among the European 

 species a short first submarginal cell and a marginal cross-vein 

 inserted about the middle of its petiole, are characters usually 

 connected with short antenna? in the male (compare Loew, 1. c. 

 p. 414) ; but the American A. megacera proves that this is not 

 an invariable rule ; although this species has a very short first 

 submarginal cell, the antenna? of the male are much longer than 

 the body. 



The male forceps does not seem to have anything unusual in 



its structure ; it consists of the ordinary basal pieces, with horny 



appendages ; I have not had the opportunity to observe it upon 



living specimens. The ovipositor of the female is remarkable for 



16 October, 1868. 



