Calvert : Odonata of the Neotropical Region. 209 



On the other hand it must be pointed out that the difference be- 

 tween the pterostigmata of the front and hind wings of the males is 

 much slighter than in males of Ischnura and perhaps than in de Selys' 

 type of nepos ; in some examples there is no difference in size and very 

 little in shape, and in all there is no difference in color. The shape 

 of the pterostigma is less oblique than in Ischnura and is not unlike 

 that of Acanthagrion truncation. The more distally situated point of 

 separation of the anal vein from the hind margin, especially on the 

 hind wings, is a divergence from Ischnurine characters, and so also is 

 the tendency of M 2 in so many hind wings to arise at a point more 

 remote than the third postnodal. The shape of the superior append- 

 ages of the male (aside from the existence of the " branche interne ") 

 is not Ischnurine, nor on the other hand does it resemble those of the 

 males of de Selys' " seconde section" of Acanthagrion, a reference 

 suggested by the venational characters. Further, it is not certain 

 whether the females above described as heterochromatic may not, to 

 some extent, represent different stages in development rather than true 

 dimorphs. 



On the whole, however, it seems best to adopt provisionally de Selys' 

 suggestion and consider nepos an aberrant Ischnura, 



The fragmentary specimen from Piedra Blanca shows an interesting 

 abnormality in the stigmata of the hind wings : the stigmata are tri- 

 angular, due to the meeting of the proximal with the distal edge at the 

 costa and the entire suppression of the costal edge ; the stigmata thus 

 touch the costa at hardly more than a point and only a slight recession 

 from the wing margin would be necessary to produce a condition es- 

 sentially like that of the stigma of the front wing of Anoi7ialagrion 

 hastatum d\ 



109. Ischnura fluviatilis Selys. 



Ischnura JluviatilisR.\s, Hamburg, Magal. Sammelr. Odon., p. 14, 1904 ; Deut. Ent. 

 Zeitschr. 190S, p. 518. 



Habitat : — Brazil, Marajo Island, Aug. -Oct., 1907, by Miss H. 

 B. Merrill, 1 d\ 2 het. 9 ; and Rio Grande do Sul, by H. v. Ihering, 

 2 $ no. T>2>2>- Academy of Natural Sciences, Philadelphia. 



Cachoeira Cuyaba, flooded campo, January 26, by H. H. Smith, 1 

 d\ Carnegie Museum, Pittsburgh. 



Paraguay, Sapucay, by W. T. Foster, November, 1899, x c? (no. 

 18), 1 9 (no. 4), February, 1900, 1 het. ?. U. S. National Mu- 

 seum. 



