d. Parts of arculus of hind wing above and l)elow attach- 

 ment of sectors nearly eqnal, the lower sector join-" 

 ing it distinctly below the middle. 

 ee. Hind femora long, reaching base of 3, with 5-7 long 

 spines besides the usual spinules. 



VII. Bromogomphus. 



e. Hind femora usually moderate, with spinules but 



no long spines. VIII. Gornphus. 



KEY TO THE GENERA OF THE NORTH AMERICAN NYMPHS OF 



OOMPHID^. 



AA. Tenth (last) abdominal very long and slender, many times 

 longer than broad, nearly half the length of the abdo- 

 men. I. ApltijJJa. 

 A. Tenth abdominal usually broader than long, never more 



than twice as long as broad. 

 aa. Middle legs approximated at base; inner pair of wing-cases 

 strongly divergent; ventral longitudinal sutures of 

 abdomen diverging to near apical angles of 8, segment 

 9 similar to 10; lateral labial lobes entire, their apices 

 rounded; 3d and 4th antennal joints subcylindric, 

 more than twice as long as thick, the latter recurved; 

 five or more pairs of lateral spines; dorsal hooks pres- 

 ent but not prominent. II. Progomphus. 

 a. Middle legs at least as far apart as fore legs; ventral lon- 

 gitudinal sutures of abdomen diverging to apical 

 angles of 9, which is unlike 10 ; 4th antennal joint very 

 short and small ; not over 4 pairs of lateral spines, ex- 

 cept in Ha genius, 

 hh. Inner pair of wing-cases strongly divergent ; 3d anten- 

 nal joint oblong, at least twice as long as broad ; lat- 

 eral labial lobes dentate, without apical hook ; tenth 

 abdominal narrowing posteriorly, following the taper- 

 ing outline of the apex of the abdomen. 



HI. Diastatonuua. IV. Ilerpetogomphus. 

 h. Inner pair of wing-cases parallel, lying close together 



