474 NEW YORK STATE MUSEUM 



and a hidden labium springs from the sand with a mighty sweep and 

 clutches it. I fed to a nymph of Cordulegaster diastatops 

 14 full grown nymphs of C apni a in rapid succession, which should 

 represent a bulk about equal to that of the nymph that ate them. It ate 

 a dozen quickly, the last two more slowly : it had been without food sev- 

 eral weeks. Nymphs of the species described below as C. maculatus 

 supposition, at Saranac Inn, captured and ate young brook trout as long 

 as themselves, when placed in their cage. So eager were they, they 

 would rise partly from the sand on approach of a trout. Like the 

 nymphs of the Aeschninae, they seem to have a decided preference for 

 big game, if one may judge by the strenuous efforts they put forth when 

 something at the limit of their capacity for capturing approaches. 

 Our species belong to a single genus. 



CORDULEGASTER Lcach 



Of the seven species occurring north of Mexico six are found in the 

 eastern United States, and of these six, five are likely to be found in New 

 York state when careful collecting is done for them. But two of these, 

 C. erroneus (from Keene valley) and C. diastatops, are on rec- 

 ord from the state ; a third, C. maculatus is recorded below from 

 Saranac Inn. 



Imagos of the six species of the eastern United States may be sepa- 

 rated by the following table : 

 a Eyes not contiguous ; the proximal inferior tooth of the superior abdominal 

 appendage of the male almost completely incased within the 10th segment 

 (subgenus Zoraena) 



h Abdomen with yellow lateral spots; stigma brown diastatops 



hh Abdomen with yellow half rings ; stigma yellow sayi 



aa Eyes contiguous; proximal inferior tooth of superior appendage of male 

 more or less completely exposed 

 l Two cubito-anal cross veins before the triangles; triangle open, or divided 

 by a single cross vein ; stigma moderate (subgenus Cordulegaster) 



c Abdomen with yellow lateral spots maculatus 



cc Abdomen with yellow half rings erroneus 



J)h Usually three cubito-anal cross veins before the triangle ; triangle often 

 divided by more than one cross vein ; stigma very long (subgenus 

 Taeniogaster) 



d Abdomen with lateral yellow spots (southern) fasciatus 



dd Abdomen with a middorsal line of spots obliq u u s 



ARTIFICIAL KEY TO THE SAME SPECIES 



a Abdomen with a middorsal line of spots obliquus 



aa Abdomen with yellow half rings on the segments 



h Face yellow sayi 



