INSECTS 



having the same essential structure as that of the horse- 

 fly (Fig. 170 A). 



The house fly has no piercing organs; it subsists en- 

 tirely on a liquid diet. The food liquid enters the aper- 

 ture between the labella, and is drawn up to the true 



Ant 



Plp- 



Prb 



Lm_ 



Hphy 



Fig. 183. Head and mouth parts of the house fly 



A, lateral view of the head with the proboscis (Prb) extended. Ant, 

 antenna; E, compound eye; La, labella, terminal lobes of the pro- 

 boscis; Pip, maxillary palpi (the maxillae are lacking); Prb, pro- 

 boscis 



B, the proboscis of the fly, as seen in three-quarter front view and 

 from below. The proboscis consists of the thick labium (Lb), ending 

 in the labellar lobes (La), between which is a small pore (a) leading 

 into the food canal (FC) of the proboscis. The food canal contains 

 the hypopharynx (Hphy), and is closed in front by the labrum (Lm) 



mouth through the food canal in the labium between the 

 labrum and the hypopharynx. The fly, however, is not 

 dependent on natural liquids; it can dissolve soluble sub- 

 stances, such as sugar, by means of its saliva. The 

 saliva is ejected from the tip of the hypopharynx, and 

 probably spreads over the food through the channels of 

 the labial lobes. These same channels, perhaps, also 

 collect the food solution and convey it to the labellar 

 aperture. 



[346] 



