32 



Nijuiphs. 



A A. Four or more pairs of lateral spines (sometimes an imper- 

 fect additional pair anterior to those here counted as 

 the first pair) ; eyes occupying less than two thirds of 

 the side margin of the head ; scale of male on base of 

 superior terminal appendage triangular, not emarginate 

 at apex. 

 aa. Five pairs of fully-developed lateral spines. 



hh. Antennae 6-jointed, the last two segments of the other 

 genera being represented by a single long joint 

 sometimes divided by an indistinct suture in full- 

 grown nymphs ; eyes small, occupying only one 

 third the lateral margin of the head ; apex of supe- 

 rior appendage truncate or feebly emarginate. 

 cc. Abdomen carinate posteriorly, forming low dorsal 

 hooks. I. Nai^iw.srhiia. 



c. Abdomen without trace of dorsal hooks. 



II. Epheschna. 



h. Antenna 7-jointed; eyes occupying about half the 



lateral head margin ; apex of superior appendage 



deeply emarginate. 



dd. Lateral labial lobes scarcely tapering, obtuse or 



subtruncate at tip, median lobe minutely 



toothed each side of cleft ; superior appendage 



not less than five sixths as long as the inferiors. 



III. Bo II e rid. 

 d. Lateral labial lobes tapering to the incurved 

 apical tooth, median lobe with a chitinous 

 callosity on each side of cleft ; superior append- 

 age about three fifths as long as inferiors. 



IV. Bihsid'schna. 



a. Four pairs of lateral spines, the anterior pair much 



smaller than the others but distinctly spiniform ; 



apex of superior appendage broadly but not very 



deeply notched ; median lobe of labium not toothed. 



V. JEschna, 



