32 
Nymphs. 
AA. 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. 
bb. Antenne 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. Nasieschna. 
c. Abdomen without trace of dorsal hooks. 
Il. Epiceschna. 
b. Antenne 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 minutel 
toothed each side of cleft; superior me | 
not less than five sixths as long as the inferiors. 
III. Boyeria. 
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. Basiceschna. 
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. A’schna. 
