24 A VENATIONAL STUDY OF THE ZYGOPTERA 



and Ilemiphlebia (fig. io6) are arrived at; the other branch devel- 

 ops by a greater petiolation, which extends to or beyond Ac in 

 those genera above Pseudagrion (fig. 114). This line continues 

 through Oxyagrion (fig. io<^) , Acanthagrion (fig. 1 10) and others until 

 a new tendency is observable, namely the movement outward of 

 the base of Ms, until the origin of this vein very nearly coincides 

 with that of R^. This is true of such genera as Nesobasis, Aciagrion 

 (fig. 123), Leptobasis (fig. 127) and Teinobasis (fig. 128). In 

 Amphicnemis (fig. 129) the base of M3 reaches thesubnodus and Rs 

 arises a cell beyond, while petiolation extends at least to the level 

 of the arculus. 



To return for a moment to the discussion of Ceratura (fig. 102), 

 Anomalagrion (fig. 97) and their allies; there are to be found here 

 several very interesting and peculiar conditions. The male of 

 Anomalagrion hastatum in the fore-wing has the stigma small and 

 three-sided, with the apex of this triangle not reaching the margin 

 of the wing, and with the base on Ri. Ceratura (fig. 102), Ans- 

 trocnemis (fig. 104) and Hemiphlebia (fig. 106) have the second 

 antenodals placed before the arculus, and have only from five to 

 seven postnodals, while Cu2 extends but a few cells beyond the 

 level of the subnodus. In Austrocnemis and Hemiphlebia petiola- 

 tion extends almost to Ac, since Ab and Ac are in line with each 

 each other. A' does not begin at the wing margin and the other 

 characters above mentioned place these two genera in this line 

 rather than in the Leptobasis one. The absence of the inner end 

 of the quadrangle in the fore-wing of the male of Ilemiphlebia (fig. 

 106) is an unusual state of affairs, and an interesting parallelism to 

 the Megapodagrionine Chorismagrion (fig. 69) recently described 

 by Morton (1914). 



The Protoneurinae 

 This subfamily, the most specialized one among all the Zygop- 

 tera, includes the legion Protoneura of de Selys. It is distinguished 

 primarily by the reduction in length of Cuo which is generally 

 represented by a cross- vein only. In fact, this character was the 

 one first used by de Selys to determine whether a genus belonged in 

 the legion or not. On the discovery oiProueiira prolongata (fig. 131) , 

 in 1889. with the vein Cuo one cell long, he modified the definition 



