VII 



MOUTH-PARTS 



443 



subject to great diversity of structure within the limits of the 

 Order itself, even the two sexes in some species differing pro- 

 foundly in this respect. 1 In the majority of the family Oestridac 

 the mouth-parts are practically absent, and no definite entry to 

 the alimentary canal can be perceived (Fig. 245). Besides this 

 condition and its antithesis (Fig. 214), the complex assemblage 

 of lancets seen in the Breeze-flies that draw blood, there is a 

 great variety of other anatomical conditions. 



FIG. 214. Mouth -parts nf 

 the common blood-suck- 

 ing fly, Haematopota 

 plurial is $. A, Viewed 

 from beneath, the pro- 

 boscis removed ; a, 

 labrum ; b, b, cultelli 

 (mandibles of other 

 anatomists) ; c, c, scal- 

 pella (maxillae of other 

 anatomists) ; d, part of 

 ventral scutum of second 

 metamere ; e, e,f,f, parts 

 of palpi ; ff, hypopharynx 

 and pellucid salivary 

 duct ; h, salivary recep- 

 tacle ; i, salivary duct ; 

 k, membranous part of 

 second metamere ; I, 

 pharynx : B, labrum, 

 pharynx, hypopharynx, 

 separated, seen from 

 beneath ; a, labrum ; b, 

 hypopharynx ; c, salivary duct ; <?, pharynx ; e, protractor muscles : C, proboscis 

 (labium) from beneath ; a, scutum proboscidis ; c, c, labella ; tl, d, retractor muscles. 

 (After Meinert). 



Although, as we have said, great diversity of opinion 

 exists, yet on the whole the majority of Dipterologists accept a 

 view something to the following effect : the labrum, or the 

 labrum combined with the epipharynx, is frequently much pro- 

 longed ; the tongue hypopharynx may also be much prolonged, 

 and may form, in apposition with the labrum, a more or less im- 

 perfect tube for ingestion of the nutriment ; the labium is more 

 or less membranous or fleshy, and acts as a sheathing organ, its 

 tips called labella being in some cases developed to a quite 

 extraordinary extent. As to the other parts of the mouth there 

 is less agreement; the pointed organs (Fig. 214, A, I 6) are by 



1 It is frequently said that one sex of a single species may be dimorphic in this 

 respect, but we shall subsequently mention (in Blepharoceridae) that this is not 

 yet sufficiently established. 



3 



