THE PUPAL STAGE OF CULEX. 57 



Beneath the fins and behind the eighth segment is the "ninth 

 segment" with its appendages. Though this region is probably made 

 up of more than one segment, its composite nature is not easy to 

 recognise, as the plates supposed in other insects to represent the 

 terga and sterna of tenth and eleventh segments [see, for instance, 

 Huxley (7) and Miall and Denny (8)] are not developed in the 

 young pupa, nor, indeed, is there in any stage any such development 

 of the pupal cuticle, though plates developed within as parts of the 

 imaginal cuticle may perhaps represent some of these parts. 



The appendages of the " ninth segment " of the pupa are a pair of 

 blunt processes arising below and in front of the anus, and directed 

 backwards below the fins. They are much larger in the male than 

 in the female. A pair of appendages are already recognisable in 

 this region in sections of the larva, and I think even two pairs, but 

 this portion of the larva is particularly difficult to cut, and I am 

 not yet certain as to the hinder of the two pairs. Of the existence 

 of one pair I have no doubt. 



The Digestive System. 



The alimentary canal of the pupa runs almost direct from end to 

 end of the body, the only convolution occurring in the region of the 

 intestine. 



In the youngest pupa the condition is practically that of the larva. 

 (See Baschke, op. cit.) The narrow oesophagus projects slightly into 

 the stomach. The stomach extends from the anterior part of the 

 thorax to the end of the fifth segment (abdominal) : it is very wide, 

 and the eight diverticula found in the thoracic region of the larva 

 are still present. The walls are very thick, and the cells of its 

 epithelium large. 



The stomach opens behind into the intestine, which is slightly 

 coiled and opens into the wide rectum, which ends at the hinder 

 end of the abdomen. The epithelium of the rectum consists of very 

 large cells, and is thrown into longitudinal folds. 



The salivary t /lauds are unbranched sac-like glands in the anterior 

 part of the thorax at the sides of the alimentary canal. Their ducts 

 unite beneath the BUb-oesophageal ganglia, and from this point the 

 single median duct runs forwards to open in the floor of the mouth. 



