104 DRAGON FLIES VS. MOSQUITOES. 



unbarbed characters of the maxillsej and by having the an- 

 tennae plumose. The mouth of the female Culex consists 

 of two groups of appendages, the elements of punctation 

 and suction, with 'which are connected the adjustments for 

 the secretion and emission of the poison, and the parts 

 which enclose these and form around them a natural 

 sheath. 



The first group, which are surgical in character, em- 

 brace the epipharynx, second, the hypopharynx, two 

 mandibles, and two maxillee; and the second group com- 

 prises the labrum (upper lip), and the labium, which re- 

 ceives them into a groove on its upper side. (Dimmock.) 

 The epipharynx is slightly attached to the labrum, and 

 this combination, termed the labrum epipharynx, tapers 

 uniformly from the base to the apex. It forms an un- 

 finished tube, being completed along its inferior surface by 

 the oppression of the hypopharynx to the narrow slit be- 

 tween its separated edges. The channel thus made is the 

 avenue by which the juices of its host passes to the oesoph- 

 agus, which is the postpharyngeal passage, and which acts 

 like a suction pump for the imbibition of the nourishing 

 liquids, being expanded into a bulb behind a valvular con- 

 striction of the pharynx. This action is performed by 

 muscles attached to the epipharynx "having their inser- 

 tions on the upper side of its wings or lateral portions " 

 and extending upward and backward over the inner sur- 

 face of the clypeus, the chitinous escutcheon above the 

 labrum. The hypopharynx is a linear lanceolate, trans- 

 parent lamellce of chitin, and is the element needed to 

 complete the tube of the epipharynx, which it effects by 

 being placed in apposition with the inferior margins of the 

 latter. Dimmock discusses the difficult question, whether 



