AQUATIC INSECTS IN NEW -YORK STATE 219 
In view of the fact that the nymphs of about half our species, 
including some of the commonest, are still unknown, a word to 
the collector, additional to what has been said in Bulletin 47, will 
be in order here: The Zygoptera are very easily reared. Nymphs 
taken when grown will transform readily in any sort of aquarium 
containing plant stems for them to climb on. Males should be 
bred for certain determination; and the male imago when well 
colored should be placed at once with its cast skin in a vial of 
70% alcohol and promptly labeled. 
But, unlike most Anisoptera, the Zygoptera transform com- 
monly in the daytime; and it thus becomes a very easy matter 
at the right time to pick up life history material. At the time 
when any species known to be locally common is just beginning 
_to appear on the wing, one may go to its aquatic haunts, expect- 
ing to find with a little searching nymphs on stems near the 
surface of the water, others crawling out or transforming, 
imagos beside their recently abandoned nymph skins and teneral 
imagos taking flight. At this time it will not do to assume that 
all that look alike are the same species. Owing to the exceed- 
ingly close likeness of many of the species in such genera as 
Lestes, Argia and Enallagma, one must select males for certain 
determination, must keep each imago with its own cast nymphal 
skin, and must keep the imago alive till the form of the ap- 
pendages and the color pattern are fully developed. This last 
point is readily secured by placing the imago and skin when 
newly transformed in a paper bag for 24 hours, closing the top 
and avoiding undue jostling about at first. 
KEY TO FAMILIES AND SUBFAMILIES OF ZYGOPTERA 
Imagos 
a Quadrangle [see fig.8] of the wings divided by 
a number of cross veins; antenodal cross 
veins numerous; pterostigma lacking a special 
brace vein; wings rather broad.....:...sssees Calopterygidae 
aa Quadrangle without cross veins; antenodal cross bs 
veins but two in each wing; pterostigma with 
a brace vein at its proximal end in the space 
behind vein Ry; wings narrower... ....ceveees Agrionidae 
