61 



The imago is one of the largest gomphids. It is black, with 

 clear wings and yellow markings, and flies along the small 

 rapid streams which are inhabited by the nymph. 



Hagenius brfristi/hts Selys. 



This grotesque nymph looks more like a colossal bedbug 

 than a dragon-fly nymph, being extremely flat and broad, with 

 a disk-shaped subcircular abdomen. It is unique in habits as 

 well as in form. It seems to prefer rapid-flowing streams, and 

 does not burrow as do other gomphid nymphs, but clings to 

 stones or to tethered drift-stuff in the current, or hides among 

 loose drift and dead leaves. Mr. Needham found nymphs of 

 three distinct sizes in a stream near Ithaca. The imagos 

 emerged all at once, and a considerable number of exuvite were 

 found. This would indicate a three-year life-period, the nymphs 

 not maturing till the third season after the one which brought 

 them into existence. We have examples taken from the upper 

 Sangamon River in Piatt county in September and October, 

 and at Chicago and Quincy. This nymph seems to be quite in- 

 frequent in Illinois. The imago occurs all over the country 

 from Maine to Texas and Kansas, and is reported (Kellicott '95) 

 as abundant in Michigan, but I am not aware that it has ever 

 been taken in this state. It flies through June, July, and the 

 greater part of August. 



In view of the excellent figures and description by Cabot 

 ('72, p. 9) and the very minute description by Dr. Hagen ('85, 

 p. 279) it will be sutiicient here to give only the more promi- 

 nent characters. 



The nymph measures in length 36 to 40 mm.; hind femur, 

 10 to 12 mm.; abdomen, 22 to 23 mm.; wadth of abdomen 20 mm., 

 of head 8 mm.; vertical thickness of abdomen about 4 mm. 



Body exceedingly flat, ovate in outline, nearly destitute of 

 hairs. 



Head cut off squarely behind; eyes a little projecting on 

 the sides, front sloping to base of antennae. Top of head with 

 a pair of conic tubercles behind the lateral ocelli and a larger 



