36 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



green. The antenodal cross-veins are never more than two in 

 number in our species and the nodus is usually from one-third to 

 one-fifth the distance from the base to tip of the wing. 



Key to Subfamilies 



Nymphs 



I. Labium much contracted at base, not triangular in outline, the 

 contracted portion as long as the expanded; gills as in Plate i. 

 Figs. 1-6, usually smoky or brown, and the tracheal branches 



inconspicuous Lestinae, p. 93 



Labium not contracted at base, triangular in outline ; gills usually 

 clear or with smoky cross-bands, the tracheae much branched 

 and frequently conspicuous Coenagrioninae, p. 36 



Adults 



I. Ms arising much nearer the arculus than the nodus or subnodus ; 

 supplementary sectors present between Rs and M3 and between 

 M3 and M4 ; anal appendages of the male f orcipate and usually 



much longer than the tenth abdominal segment Lestinae, p. 93 



Ms arising much nearer the nodus or subnodus than the arculus : no 

 supplementary sectors between M3 and M4 ; anal appendages of 

 the male not forcipate and not exceeding the tenth abdominal 

 segment in length Coenagrioninae, p. 36 



Subfamily Coenagrioninae Kirby 



The nymphal gills differ from those of the Agrioninae and 

 Lestinae, usually possessing more conspicuous tracheae. The 

 abdomen is less slender, and the median lobe of labium is more 

 nearly triangular and not greatly contracted, proximad in our 

 species. 



Adults of the subfamily are usually marked with stripes or 

 spots of blue, or yellow, but a few species are uniform metallic 

 green above. The wings contain fewer irregular cells than the 

 Lestinae and nearly all primary veins are straight almost to the 

 margin of the wings. 



Key to Genera 



Nymphs 



1. Gills half as broad as long; labium without mental setae Argia, p. 85 

 Gills not more than one-third as broad as long; labium provided 



with mental setae 2 



2. Caudo-lateral angles of the head projecting and forming a blunt 



tubercle, the margins of the head much contracted between the 



tubercles and the eyes 3 



Caudo-lateral angles of the head not projecting and forming a 

 blunt tubercle ; the margins of the head not contracted between 

 the tubercles and the eyes 4 



3. Gills without cuticular pigment; one-third as broad as long, the 



margins thickly provided with heavy setae which extend from 



the base to the apex of each Amphiagrion, p. 48 



Gills with considerable cuticular pigment; not more than one-sixth 

 as broad as long, the margins sparsely setose (PI. 11, Fig. 2) 



Chromagrion, p. 46 



