THE DIPTERA. 



369 



As in JTemiptera, also, the labrum is a more or less elongated 

 pointed plate, and the mandibles and maxillae are usually ter- 

 minated by chitinous cutting setae (Fig. 109). But the bases 

 of these parts are constantly united together ; there is a pair 

 of maxillary palpi, and often a median, more or less styliform 

 structure, usually considered to be the hypopharynx. It 

 seems doubtful, however, whether this ma}' not be formed by 

 the coalesced terminations of the maxillae. In the common 

 House-fly, the labrum 3 mandibles, and maxillae coalesce at 



Fig. 110.— Upper figure. Section of the head of Bombns. 5, ocellus ; c, antenna ; d, 

 clypeus ; e, labrum ; /, mandible ; g, epipharynx ; h, maxilla ; i, cardo ; ,;, k, I, 

 6ubmentum and mentum : m, m', labial palpus ; w, paraglossia ; o, lingua or 

 median process of the ligula ; «, occipital foramen ; 1, 2, sclerites of the hypo- 

 pharynx. 



Left lower figure. Terminal portion of a maxilla. 



Middle lower figure. Epipharynx and hypopharnyx magnified ; 1, 2, sclerites of 

 the hypopharynx; 3, cut end of tlie oesophagus; 4, 5, sclerites in the wall of the 

 oesophagus and sides of the mouth; 6, lip-like projection of the hypopharynx; 

 g. epipharynx. 



Right lower figure, a, quadrate sclcrite connected by a triangular piece with c, one 

 of the lances of the sting: b, duct of the poison-gland ; f, grooved median piece 

 in which the lances play; h, one of the lateral setose palpiform sheath-pieces; g, 

 genital aperture. 



their origins to constitute the base of the proboscis, which is 

 mainly formed by the confluent second maxillae. Its longitu- 



