loy 



4. Draw the body of the mosquito away 

 from the separated segments ; the mid- gut and 

 sundry other viscera will be left attached to the 

 latter floating in the salt solution. 



Observe that when the tension is relieved, 

 the structure last to leave the abdomen of the 

 mosquito assumes a saccular appearance. This is 

 the mid-gut. 



The Viscera 



(F'g- 30) 



1. Unless the mosquito is newly hatched, 

 note two opaque white oval bodies (the ovaries) 

 attached to the separated segments. If the 

 ovaries are near maturity, masses of white ova 

 are seen. 



2. The Mid-gut. — This extends from the 

 level of the first pair of legs to the posterior 

 border of the sixth abdominal segment. 



(i) An anterior narrow portion resembling 

 an oesophagus. 



(ii) A posterior dilated portion at the level 

 of the sixth (and fifth) abdominal segments in 

 which, if the last meal of blood is not quite 

 digested, a black mass will be seen. If any blood 

 remains in this portion, i.e., ' the stomach,' dis- 

 card the specimen for one kept longer without 

 food. 



(iii) At the commencement of the mid- gut 

 a ring-like, thickened portion (the proventriculus). 

 It acts as a valve between the oesophagus and 

 mid-gut (Fig. 30). 



3. Passing between the mid-gut and the 

 separated segments, note five brilliantly white 

 threads — the malpighian tubules (Fig 30). 



