THE HOUSE-FLY 



"bite." The proboscis (Fig. 6) can be protruded and 

 retracted to a certain extent. Roughly, the proboscis 

 consists of two parts, a part nearest the head that bears 

 two short curved appendages, and a longer part farthest 

 from the head that bears two lobe-like appendages called 

 the oral lobes. Each lobe bears 

 on its under surface many trans- 

 verse ridges called false tracheae 

 (pseudotracheae) . These lobes 

 are rasping organs. Each lobe 

 reminds one of an old-fashioned 

 shoe float formerly seen in stores 

 and used for removing the ends 

 of wooden pegs that projected 

 through the soles in the inside 

 of a shoe. When feeding on 

 fluid substances the fly simply 

 applies the oral lobes to the 

 material and sucks it up. When 

 feeding upon solid substances 

 the action is quite different. If 

 such a substance as sugar is eaten, for example, it 

 is first moistened and dissolved by saliva from the 

 mouth of the fly before it is sucked up. The oral 

 lobes also serve to rasp the material and break it 

 down. 



Graham-Smith watched a fly sucking a mass of sputum 

 that had apparently dried and hardened. The insect 

 seemed to moisten the layer of sputum by sending out 

 saliva through its proboscis and sucking the fluid in and 

 out until the layer was liquefied and could be drawn up 

 into the mouth. 



Fig. 6. — Head and proboscis 

 of house-fly. ( X 20.) 



