TOE DIPTERA. 



300 



As in Hemiptera, 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, usuaHy considered to be the hypopharynx. It 

 seems doubtful, however, whether this may not be formed by 

 the coalesced terminations of the maxillae. In the common 

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



FIG. 110. Upper figure. Section of the head of Bombus. 6, ocellus ; c, antenna : rf, 

 c'.ypeus; 0, labrum; /, mandible; g. epipharynx; A, maxilla; /, cardo ; j< *, /, 

 tnibmentum and mentum ; m, w', labial palpus ; n, parairlossa ; o, lingua or 

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

 pharynx. 



Left !<>\vor flirnro. Terminal portion of a maxilla. 



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

 tli<> hypopharynx; 3. cut ond of H>e oesophagus; 4, 5, sclerites in the wall of the 

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

 rj. epipharynx. 



Right lower figure, n, quadrate srlerito connected by n triancular piece with o. one 

 of the lances of the stin^ : A, duct of the poison -sriand ; /. grooved median piece 

 in which the lances play; A, one of the lateral petose 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- 



