THE DIPTERA. 



369 



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

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

 minated by cliitinous cutting set^e (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 maj' not be formed by 

 the coalesced terminations of the maxillae. In the common 

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



Fig. 110. — Upper flf::nre. Section of the head of Bomhu^. ft, ocellus ; c, antenna ; rf, 

 clypeus; e, labrum; /, mandible; g. epipharynx ; A, maxilla; ?', cardo ; j, k, I, 

 Bubmentum and nientum ; m, m'. labial palpus ; n. para^rlossa ; o, lingua or 

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

 pharynx. 



Left lower flgure. Terminal portion of a maxilla. 



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

 the hypopharynx| 3, cut end of tl>e oesophaniis; 4. 5, sclerites In the wall of the 

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

 (f. epipharynx. 



Right lower figure, a, quadrate sclprite connected by a triangnlar piece with c, one 

 of the lances of the sting; 5, duct of the poison-eland ; f, grooved median piece 

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

 genital aperture. 



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

 mainly formed by the confluent second maxillae. Its longitu- 



