652 Wisconsin Academy of Sciences » Arts and Letters. 
helpless in the water with unexpanded wings, hut valuable for 
preservation. I was able by means of the exuvia to positively 
connect the larval and pupal stages in this case. 
It was my original intention in working up the life-histories 
in this paper, to give descriptions only of the immature stages, 
except in the case of new species. Before working long with 
McLachlan’s excellent monograph, however, it became evident 
that many of our species needed more complete descriptions,— 
this being especially true of the species described by Walker. 
Particularly, the male genitalia should be described and figured. 
I have, therefore, for the sake of completeness, and, I hope, 
greater accuracy, written new descriptions of the images and 
made accompanying drawings. The drawings of the male geni¬ 
talia, in the interests of accuracy, have been made from 
material preserved in alcohol or formalin, since with such speci¬ 
mens the parts may be moved about and carefully studied with 
a binocular dissecting microscope. I have not consciously copied 
from the old descriptions, nor have I, on the other hand, taken 
extreme pains to avoid the use of the same terms there em¬ 
ployed. I at first attempted to use as much as possible of the 
old descriptions, giving proper credit, but this proved to be a 
cumbersome and tedious method, and it was therefore aban¬ 
doned. 
In the descriptions of adults, when the spur number is not 
given, it is the same as the number typical of the genus. 
Length of body is apt to be unsatisfactory, owing to shrinkage, 
yet it is worth more than length to tip of wings,—when expanse 
is also given,—since the latter is very nearly half the expanse 
in all cases, while the relative length of body and wings may 
be quite different. 
On some of the dorsal abdominal segments of the pupae are 
certain paired chitinous plates bearing spines or hooks. On 
all of the segments thus armed one pair near the anterior bor¬ 
der of the segment bears backwardly directed hooks. On one 
segment (in a few genera, on two or three) there is in addi¬ 
tion, on the posterior border of the segment, a pair of plates 
which bears hooks directed forward: this is in most cases the 
fifth segment. Although the number of these hooks to each 
