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The labium consists of the following parts : — 



Submcnlum. — The submeutum is the proximal part of the 

 labium. It is nearly crescent-shaped, and is joined to the 

 membrane which connects the head with the thorax. 

 , NOTE. — It is believed by some writers tbat this crescent-shaped 

 part is composed of two fused sclerites, and that the caudal portion of 

 it represents the gula. 



Mcntum. — This is the central portion of the labium ; and 

 is the principal part of that organ. It is articulated to the 

 distal margin of the submentum. To the distal margin of 

 the mentum are joined two movable flaps ; and to each 

 lateral margin is joined an organ consisting of three segments. 



Labial Palpi. — These are the three-jointed organs of which 

 one is joined to each lateral margin of the mentum. 



Palpiger. — The labial palpi are not joined directly to the 

 mentum. There is on each side of the mentum a sclerite 

 which bears the palpus of that side and which is called the 

 palpiger. The suture between the palpiger of each side and 

 the mentum is almost obsolete. Its position is indicated by 

 a slight groove which causes the palpiger to appear some- 

 what like a segment of the palpus. 



Lignla. — This is the distal portion of the labium. It con- 

 sists of two large movable flaps. 



Hypopharynx. — If the specimen has become dry so as to 

 be brittle, it should be softened with a little water. 



With the specimen pinned as in last section, carefully lift 

 the ligula so as to expose the maxillae. Note the tongue- 

 like organ which arises from the labium and from between 

 the maxillae. This is the hypopharynx. 



Remove the labium and place it on a glass slip in a drop of 

 Canada balsam or glycerine and cover it with a cover glass. 

 Examine it with a microscope using a low power. Make 

 a drawing of the caudal aspect of the labium, and letter the 

 parts. 



Study the distal end of the distal segment of a labial palpus 



