74 DRAGONFLIES OK OHIO. 



FOURTH SUB-FAMILY. 



CORDULEGASTERlK/E. 



The members of this sub-family are all large 

 insects. Less than ten species have been described 

 from America north of Mexico. None of these seem 

 to be common, so far as individuals are concerned, at 

 least they are not often taken. I have seen so few 

 specimens on the wing- that I do not feel justified in 

 giving anything of their habits in the field. 



CORDULEGASTER, Leach. 



Two species have been taken in the state ; they 

 may be separated as follows : 



1. Large species, abdominal segments 2-7 nearly encircled by yellow, 



erroneous. 



2. Smaller species, yellow on abdomen takes the form of spear- 

 shaped markings on the dorsum of segments 2-8 ohliquus. 



Cordulegaster erroneous, Hagen. 



Length of abdomen d 53-56, 9 62, hind wing c? 44- 

 47, 9 50. 



Female; colors black, brown and yellow. Head; 

 anterior part of vertex, nasus, gense, disk of labrum, 

 and labium, yellow • occiput yellow behind, brownish 

 yellow in front, ciliated above with long yellowish 

 hairs; remainder brown. Thorax; in front two oblique 

 bands pointed below and abbreviated at both ends, on 

 each side two oblique bands abbreviated at the ends, 

 and a spot above between them, the posterior ventral 

 surface and a spot between each pair of wings yellow, 

 remainder black ; legs and feet black ; veins of wings 

 and pterostigma black. Abdomen, a ventral and a 

 lateral spot each side on 1, a transverse median band, 

 oblique on the sides and continued by the ventral 

 spots on 1, and a ventral and lateral spot distally 



