ODONA TA 



323 



facilitate comparison with figures of wings of Anisoptera. In certain 

 other members of this subor- 

 der the quadrangle is divided 

 into several cells by cross- veins 

 (Fig. 37i). 



The cubital area of the 

 wing is usually quadrangular 

 in outline in the Zygoptera, 

 and is termed the subquad- 

 rangle (Fig. 369, sq). Like 

 the quadrangle, it may con- 

 sist of a single cell or it may 

 be divided by cross-veins (Fig. 

 371)- 



The naiads of damsel-flies have three plate-like tracheal gills at 

 the caudal end of the body (Fig. 372). The structure of these gills 

 is illustrated by Figure 373 ; at A is represented an entire gillshowing 

 the trachea; and at B, part of a gill more magnified, showing both 

 tracheae (T) and tracheoles (t). 



Fig. 371. 



of wing of He.'cprina. 



Fig. 373. — Tracheal gill of a damsel-fly: 



A, entire gill showing the tracheae; 



B, part of gill more magnified , show- 

 ing both tracheae (T) and tracheoles 

 (t). 



Fig. 372. — Naiad of a 

 damsel-fly, Argia. 



The suborder Zygoptera includes two families, the Agrionidee 

 and the Coenagrionidas. The genera and species of these families are 

 enumerated by Muttkowski ('10). The two families can be separated 

 as follows. 



A. Wings with many, at least five, antenodal cross-veins Agrionid.-e 



AA. Wings usually with only two antenodal cross- veins, rarely with three or 

 four CCENAGRIONID/E 



