414 MORPHOLOGY OF THE ABDOMEN IN THE ODONATA 



The Alimentary Canal 

 (Plate XXV, figure 19) 



This tract is almost perfectly straight and but little dilated in its 

 various parts. Throughout its abdominal portion it is surrounded 

 by a sheath of fatty tissue. When this is removed the following 

 parts can be made out. 



The Oesophagus is a slender tube throughout the prothorax and 

 the greater part of the mesothorax. In the latter it turns ventrad 

 and expands into the bulbous portion of the crop. A decrease 

 occurs again in the posterior part of the metathorax and through 

 the first four segments of the abdomen the crop is straight and of 

 uniform diameter, about twice that of the oesophagus. 



The Gizzard is in the first half of the sixth segment of the male 

 of Calopteryx and the fifth in the female; in the middle of the 

 sixth in Megaloprepu!^ female. It seems alike in all cases: 

 there is no dilation and the invagination of the ventriculus is 

 slight. Miss Higgins (1901) notes some variation. 



The Ventriculus is swollen moderately at the anterior end (seg- 

 ment five) and then falls to a uniform tube the size of that in the 

 anterior abdominal segments. The Malpighian Tubules are 

 received in the anterior part of the eighth segment in all species, 

 they are neither numerous nor long. 



The Ileum is dilated to egg-shape form, largest at the fore end, 

 and possesses internally six longitudinal and irregular folds or 

 ridges. It just passes the suture between segments eight and 

 nine. 



Here another enlargement, the rectum, begins. It continues 

 through segments nine and ten, and is more oblong than the 

 ileum though about the same size. In Megaloprepus especially 

 it possesses three wide, white longitud nal thickenings with thin 

 areas between; the rectum is also larger than the ileum. Near its 

 end the rectum turns ventrad to the anus, a slit-like, bristlj' 

 opening. 



The Reproductive System 

 (Plate XXV, figure 24) 



Male: — The Testes of Calopteryx extend from the anterior part 

 of segment seven to the end of eight. Thej^ lie dorso-laterally 



