— 7o — 



and epipharynx fused). It is rather bluntly tipped and -is 

 the broadest of the stylets. The fiat, smooth, sharply 

 pointed mandibles lie just above the less strongly chitinized, 

 narrower, and finely-marked maxillce. Corresponding some- 

 what to the labrum but less broad and strong, is the sixth 

 stylet, an unpaired slender piece lying below the maxillae. 

 This is the greatly developed hypopharynx* These six 

 stylets, labrum, mandibles, maxillae, and hypopharynx are 

 the instruments with which the female horse-fly pierces the 

 skin of animals to get at the blood ; the male has no pierc- 

 ing stylets, and feeds on flower-pollen. 



Beneath the grouped stylets, is the long trunk- or proboscis- 

 like labium, presenting on its upper surface a shallow fur- 

 row in which the stylets may be partially enclosed, and 

 presenting at its distal extremity a conspicuous, expanded, 

 disk -like part called the labella. This terminal disk is be- 

 lieved to be composed of the greatly modified labial palpi. 

 It is made up of two, fleshy lobes or leaves, bearing on the 

 outer or under surface many, fane, transversal, subparallel 

 lines or ridges. The two lobes can be closed together like 

 the leaves of a book. 



Make a drawing showing all' of the mouth-parts from the 

 dorsal view. The stylets can be spread apart laterad, so as 

 to expose the under ones. 



In only a few families of Diptera are free mandibles pres- 

 ent, and when present they are possessed-^only by the fe- 

 males. In many flies there are no piercing stylets, and as 

 representative of these flies without piercing mouth-parts 

 the common house-fly may be studied. 



*The hypopharynx is merely an outgrowth from the lower wall of the pharynx, 

 and is not, as are the other mouth-parts, a true appendage of the head homologous 

 with the body appendages (legs). The hypopharynx and epipharynx (outgrowth 

 from the upper wall of the pharynx) are in most insects small, fleshy, and incon- 

 spicuous. 



