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 brevistylus 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 
Joose 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 exuvie 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 al] 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 (’S5, 
p. 279) it will be sufficient 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.; width 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 antenne. Top of head with 
a pair of conic tubercles behind the lateral ocelli and a larger 
