INSECTA : DIPTERA 329 



Type : The Common House-fly (Musca domestica). 



These flies are only too well known to all and are justly 

 disliked on account of their habit of feeding on our food and 

 soiling everything on which they settle, a 

 habit more dangerous to us than is gener- 

 ally realised, for flies are now known to be 

 the means of distribution of many poisonous 

 germs. 1 Their irritating buzz is produced 

 by the vibration of their wings. The flies 

 found in houses belong to several different FlG - 246. Antenna 

 species. Musca domestica, which is most 

 abundant in the late summer, can be dis- 

 tinguished by the four black streaks which run longitudinally 

 over the front part of the thorax, and by the single streak 

 along the back of the abdomen. The rest of the body is 

 greyish in hue, except for the base and under side of the 

 abdomen which are mostly yellow. 



The Head ^ e ^ ea( ^ bears two large compound eyes, three 

 simple eyes in front, very small but character- 

 istic antennae (Fig. 246), and below, the peculiarly modified 

 trunk or proboscis. This proboscis is a tube, formed appar- 

 ently from the labrum and labium, the mandibles and 

 maxillae being absent ; hence these flies cannot sting as do 

 those in which these parts are present as needle-like, piercing 

 organs. In front the proboscis bears 

 two small unjointed palps, and 

 its tip is expanded into two lip- 

 like pads (Fig. 247, p), which are 

 traversed by many small canals. 2 

 When feeding on any solid matter, 

 such as a lump of sugar, saliva is 

 "~ discharged from the mouth and 

 FIG. 247. passes down the tube into these 



A, Head of a fly from the side; B, canals, and on to the outer surface 

 proboscis seen from in front ; o f the pads. These are then rubbed 

 f Pr " over the surface of the sugar, which, 

 being dissolved by the saliva, can 

 then be drawn up by the proboscis into the mouth. When 



1 See House Flies and How they Spread Disease, by C. G. Hewitt, D.Sc. 

 (Cambridge Manuals). 2 See Schrneil's Textbook of Zoology. 



