567 



with a broad black band from the base to the apex which is widened 

 subapically, and a narrow apical ring ; terga 3-7 with small dark spots 

 near the cephalo-lateral angles, broad dorsal longitudinal stripes, nar- 

 rowed at the base but not to a line, and widened at the apex but not 

 reaching the lateral margins of the sclerites except on terga five, six. 

 and seven; terga 7-10 with pale lateral margins and black dorsal 

 stripes, the stripes narrowed at the caudal end; anal appendages of 

 the usual type ; ovipositor short, brown, the prostyles short and blunt, 

 the eighth sternites at the base of cephalic pair of gonapophyses 

 large and subtriangular ; sterna 2-7 black, the eighth with a black 

 median line but without an apical spine. 



Measurements 



Length, $ 35 mm. 



Length, 9 36 mm. 



Length of abdomen, $ 29 mm. 



Length of abdomen, 2 30 mm. 



Length of hind wings, $ 21 mm. 



Length of hind wings, S 22 mm. 



Width of hind wings, S 4 mm. 



Width of hind wings, 5 4 mm. 



Described from a number of specimens in the collection of Mr. 

 E. B. Williamson. Reported from northern Illinois by Needham 

 ('03:247). 



Genus Ischnura Charpentier 



The nymphs of this genus have gills with long tapering points 

 and one or more arcuate cross-bands. The labium is moderately 

 broad and the median lobe possesses four or five setae and five or 

 six, usually six, lateral setae. 



The adults may be distinguished from other genera by the pres- 

 ence of postocular spots, by the origin of vein M 2 , which is between 

 the third and fourth postnodal cross-veins in the front wing and be- 

 tween the second and third in the hind wing, and by the presence in 

 the males of a short apical projection of the dorsum of the tenth 

 tergum, which is, however, not as long as the segment. The sternites 

 at the base of the cephalic pair of gonapophyses of the female are 

 very small and do not project beyond the caudal margin of the large 

 basal sternite of the eighth segment. The parameres of the male do 

 not extend caudad to the margin of the ninth segment and the anal 

 appendages are short, the superiors being about as long as, or shorter 

 than, the inferior appendages. 



