AQUATIC INSECTS IX 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 



n Quadrangle [see fig.8] of the wings divided by 

 a number of cross veins; antenodal cross 

 veins numerous; pterostigma lacliing a special 



brace vein; wings rather broad Calopterygidae 



da Quadrangle without cross veins; antenodal cross 

 veins but two in each wing; pterostigma with 

 a brace vein at its proximal end in the space 

 behind vein Ri ; wings narrower Agrionidae 



