30 



KEY TO THE GENERA OF ^SCHNID^ OF THE UNITED STATES. 



Ima(j<)S. 



AA. Upper part of arculus equal to or longer than its lower 

 part, its upper sector arising near the lower sector and 

 far distant from the median vein alcove ; anal loop evi- 

 dently 5-7-sided. 

 aa. Supplementary sector, just back of the usually forked 

 radial (subnodal) sector, nearly straight and sub- 

 parallel to it, separated from it by one or two (rarely 

 three) rows of cells. 

 hh. Radial sector forked near the middle of its length ; 

 first anal vein leaving the l)order of the anal loop 

 at its hrst angulation, border continued by a cross- 

 vein which usually meets an apparent fork of the 

 second anal ; bottom of the loop accordingly 3-sided, 

 the part formed by the first anal short, not longer 

 than the remaining distance to the stem of the 

 second anal. 

 cc. Anal loop sub-oval, much as in Marroniia, wide but 

 not deep, with a row of, usually, three cells bor- 

 dering the anal vein, and a second irregular row 

 along the bottom of the loop ; triangles 3-celled 

 (rarely 4-celled ) , inner side not receiving a cross- 

 vein ; supratriangular spaces with 2 or 3 cross- 

 veins. I. Nasicpschna. 

 c. Anal loop deep, transversely oblong, with two (rarely 

 three) vertical rows of cells, ending in two or 

 three cells on the anal vein ; anterior wings with 

 discoidal triangles 5-7-celled, the inner side 

 receiving a cross- vein, and the supratriangular 

 space with 4 or 5 cross-veins. II. Epursrlnui. 

 b. Radial sector not forked ; bottom of anal loop normally 

 2-sided, one of these sides much longer than the 

 other, formed by the base of the first anal, the other 



