2 8o Annals Entomological Society of America [Vol.1, 



i) Veins Ml-3 and M4 separate at their departure from 



the arcuhis in the forewing Oxygastra 



ii) Veins Ml -3 and M4 fused a Httle way beyond the ar- 



culus in the forewing Neocordulia 



cc) Anal loop widened at its distal end and truncated more or less 

 xmsymmetrical, the hind angle being produced sensibly 

 toward the adjacent wing margin. Triangle of the hind wing 

 always retracted as far as the level of the arculus. 

 d) Veins Ml-3 and M4 fused beyond their departure from the arcu- 

 lus; cells along the middle of the anal loop divided by the 

 bisector very unequally, those lying on the cubital side being 

 much narrower. Vein M3 distinctly undulate behind the 

 nodus; median supplement distinctly developed in the fore 

 wing; supertriangle with crossveins. 

 e) Veins Ml-3 and M4 fused into a straight stalk at their depart- 

 ure from the arculus Pentathemis 



.ee) Veins Ml-3 and M4 strongly arched forward at their depart- 

 ure from the arculus. 

 f) With more than 10 antenodal crossveins: superior appenda- 

 ges of the male forcipate Aeschnosoma 



ff) With 10 or fewer antenodal crossveins; appendages of the 



niale not forcipate Libellulosoma 



dd) Veins Ml-3 and M4 not fused in the forewing at their departure 

 from the arculus: vein M3 straight or regularly arcuate behind 

 the nodus. .Supertriangle free from crossveins. 

 e) Veins M4 and Cul divergent to the wing margin. 



f) Bisector of the anal loop furcate at the slightly unsymme- 



trical widening of distal end Platycodulia 



ff) Bisector of the anal loop running into the posterior pro- 

 longation of the very unsymmetrically widened distal 



end Neurocordulia 



ee) Veins M4 and Cul not divergent to the wing margin, usually 

 slightly convergent, 

 f) Hind angle of hind wing rounded in the male: vein M4 more 



or less broken Hemicordulia 



ff) Hind wings angulate in the male. 



g) 2nd cubito-anal crossvein present in the hind wing (there- 

 fore, the subtriangle present). 



h) wings spotted Epitheca 



hh) Wings clear Somatochlora 



gg) 2nd cubito-anal crossvein (and therefore also the sub- 

 triangle) absent in the hind wing, 

 h) Triangle of the forewing traversed by a crossvein. 

 i) Wings spotted with brown. 



j) Triangle of the hind wing traversed by a crossvein, 



Epicordulia 

 jj) Triangle of the hind wing open. 



k) Antenodals of the hind wing 6 Helocordulia 



kk) Antenodals of the hind wing 4 or 5. . Tetragoneuria 

 ii) Wings clear. 



j) Antenodals about ec|ual in number to the postnodals 



in the forewing Cordulia 



jj) Antenodals decidedly more numerous than the 



postnodal s in the forewing, Procordulia and Paracordulia 

 hh) Triangle of the forewing open Dorocordulia 



