8 A VENATIONAL STUDY OF THE ZYGOPTERA 



therefore of considerable importance phylogenetically. Hence, 

 while it is not now one of the Zygoptera, it deserves discussion in 

 this paper. 



Aside from its venational primitiveness it has been shown by 

 Schmidt (1915) to be intermediate between the two modern sub- 

 orders in the structure of the male genitalia of the second and third 

 abdominal segments. Mr. Kennedy informs me that this is so 

 •obviously the case that only a separate suborder will suffice to 

 show its points of difference. The broad area between M4 and Cui 

 just beyond MA; the shape of the quadrangle, especially that of 

 the hind wing where a cross-vein in the right position would give 

 the supertriangle and triangle of the Anisoptera the zigzag con- 

 dition of the supplementary sectors, — all these are venational fea- 

 tures which justify its position as something quite distinct from 

 the Zygoptera. In itself it does not need to be taken as a form from 

 which the Zygoptera and Anisoptera have descended, in fact it can- 

 not be so considered, but it does show affinities with both and, as a 

 survival of the ancestral group from which our two modern sub- 

 orders have sprung, it is worthy of note. 



The Zygoptera Proper 



The Zygoptera may therefore evidently be considered as deriva- 

 tives of the Anisozygoptera. They may themselves be divided 

 into two families, which were long made subfamilies by workers on 

 Odonata. It would be very desirable and lead to much less con- 

 fusion if these families could retain the old names; Calopterygidae 

 and Agrionidae, but since most writers on the group have recently 

 followed Kirby's Catalogue in using the genus names Agrion and 

 Coenagrion rather than Calopteryx and Agrion, and since Mutt- 

 kowski (1910) has brought additional evidence to show that these 

 are the names to be used, I shall follow their example and speak of 

 the old group Calopteryginae as Agrionidae and of the former 

 Agrioninae as Coenagrionidae. 



Of the generic names proposed, about one hundred and eighty 

 now seem valid and are recognized in the keys hereto appended. 

 Of these about forty come in the first family, the Agrionidae, 

 which is the more generalized of the families and ends in forms 

 very closely related to some of the Coenagrionidae. The two 



