2 University of Michigan 



in 1909 by Ris,'', though, in the latter case, the species was not 

 described and named till 1913." De Selys' specimens were 

 females ; Xeedham had a single imperfect male of which only 

 the wings were preserved ; and Ris had two females. De 

 Selys' and Needham's material came from Brazil ; Ris's speci- 

 mens were from Argentina. 



The fact that no other material which might be referred to 

 Agriogomphus has come to light, is evidence of a sort for the 

 correctness of the determinations by Needham and Ris. But 

 this evidence is weak because of the scanty material. 



Ris's papers do not state that he had studied de Selys' 

 type, and his reference, in 191 3, to the type as a male (it is 

 really two or more females) indicates that he had not studied 

 them. jMoreover his failure to comment on the differences 

 shown by his specimens from the type females, as described 

 by de Selys, makes it seem possible that his determination was 

 based on Needham's figure. For there is no question that the 

 specimens studied by Needham and Ris are congeneric, 

 though there are differences in the triangles.. 



Comparing Needham's and Ris's material with de Selys' 

 description of the genus, a striking difference is detected in 

 the stigmas, — long, covering four to five cells (de Selys) ^; 

 moderate, covering two and one-half cells (Needham, Ris). 

 The distinctly four-sided triangle of the front wings (Ris) 



« Coll. Zool. Selys-Longchamps. Libellulinen. Fasc. IX, p. lo, fig. i. The 

 wings figured are those of the type described and named in 1913. 



"' Odonatenfauna von Argentina. Mem. Soc. Ent. Belg., Vol. XXII, pages 



55-102- 



8 Under the description of the species, Agriogomphus sylvicola, de Selys says, 

 "la reticulation extrement simple," and under the generic description it is stated 

 that the antenodals of the front wing number twelve. For such an insect to have 

 a stigma covering four to five cells is very remarkable and a misprint might be 

 suspected. But nothing is said of this in his corrections published four years 

 later, and in the specific description he again refers to the long stigma. 



