394 MORPHOLOGY OF THE ABDOMEN IN THE ODONATA 



Male: (plate XXI, figure 3). The testes extend throughout the 

 seventh and eighth segments. They are irregularly cylindrical 

 and attached along the dorsal edge of the visceral sheath where it 

 lies open caudad of the sixth segment. A pair of tracheae occupy 

 the dorsal and ventral lines of the testis and their lateral branches 

 form a network over the whole organ. The diameter of the gland 

 is about .5 mm. and its length nearly 3 mm. The vasa deferentia 

 are short and curve directly caudad and ventrad about the rectum 

 to a sperm sac the size of the last abdominal ganglion which lies 

 in the median line just posterior to the center of the ninth seg- 

 ment. This sac is markedly cordate in outline when viewed from 

 above and is flanked by the ^'entral Retractor Muscles of the Anus 

 and the dilators of the rectum. The two posterior branches of the 

 nerve cord as they diverge pass tangent to the antero-lateral 

 portions of the lobes, and dorsal to them. There is no enlarge- 

 ment of the vasa deferentia as they run beneath the muscles into 

 the sperm sac. The dorsal trunks (tracheae) lie just outside of 

 and slightly below the testes. The genital pore open to the ex- 

 terior beneath the sac. 



Female: (plate XXI, figure 2). The Ovaries of the full grown 

 Lestes larva are cord-hke structures lying mid-dorsally upon the 

 visceral sheath from the posterior part of the metathorax to the 

 posterior part of the seventh segment. The dorsal blood vessel 

 separates them a little. They are bound to the sheath, to one 

 another, and to the heart by fine tracheal branches. They are 

 thickest in the fifth and sixth segments and taper each way, ending 

 in attenuated points in front. In the posterior part of the 

 seventh segment they diverge and, gradually decreasing in 

 diameter and flattening out, disappear beneath the visceral sheath 

 as oviducts. If the intestine is severed at the anus and turned 

 forward, the oviducts may be traced beneath the outer posterior 

 corners of the sternal muscles of segment seven and into an oval 

 bursa copulatrix or seminal receptacle immediately posterior to 

 the last ganglion. The receptacle is somewhat larger than this 

 ganglion, and lies in the fork between the posterior nerve 

 branches. Arising from the dorsal surface of the oval sac is a 

 much larger trilobed diverticulum. Not being filled at this stage 

 in the life history, it is compressed laterally by surrounding organs. 

 A duct leads to the genital pore which opens posterior to the bursa 



