496 



NEW YORK STATE MUSEUM 



Helocordulia is most nearly allied to Tetragoneuria. 

 There are however a few venational characters which readily distinguish 

 the two genera. 



CHARACTER 



TETRAGONEURIA 



HELOCORDULIA 



2d cubito-anal cross vein 



absent 



nearly always present 



Under the stigma 



a single cross vein fol- 

 lowed by a wide space 



two cross veins and more 

 normal spaces 



Autenodal cross veins of 

 the hind wing 



four or five 



six 



The anal loop is slightly wider and more oblique at the apex in Tetra- 

 goneuria. T. spinosa has the antenodal cross veins spotted with 

 fuscous much as in Helocordulia. 



The nymph of Helocordulia is peculiar among the known cor- 

 duline nymphs in having dorsal hooks on segments 6-9 only, with some 



^ ±3^ k 



Fig. 21 Helocordulia, genitalia: x,y {$) and z ( $ ) of H, uhleri Selys: a, b (ventral 

 view), c ( ^ ) andd ( $ ) of H. selysi Hag. 



of these distinctly cultriform, and in the extreme abbreviation of the 

 ninth abdominal segment on the dorsal side, so that its dorsal length is 

 less than half its ventral. 



The two species of the genus may be separated as images by reference 

 to the figures herewith presented. The nymph is known for but one of 

 these, H. uhleri, the only one apparently belonging to the New 

 York fauna. 



