NOTES 



NOTE ON THE REACTION OF THE HOUSE-FLY 



TO AIR CURRENTS 



F. ALEX. McDERMOTT 

 Mellon Institute, University of Pittsburgh, Pittsburgh, Pa. 



While making some experiments on the drying of certain vege- 

 table materials in a current of air, the following observation was 

 made, which may be of interest. 



The material had a strong attraction for flies, of which there 

 were several in the room, and as their presence did not interfere 

 with the work, no precautions were taken to screen them off. 

 The apparatus consisted of a flat bottomed aluminum dish, 

 20 cm. in diameter, with vertical sides 8 cm. high; into this dish 

 was blown a current of air having a volume of about one-fourth 

 to one-half cubic meter per minute, by means of an electric 

 hair-drier (speed equals about 100 meters per minute). The air 

 was slightly heated, showing 29 to 30° C, when the room tempera- 

 ture was 26 to 27° C. The air current struck the center of the 

 bottom of the dish at an angle of 60°, passing over two 5 cm. 

 aluminum dishes, in which the material being dried was contained. 

 Flies alighting on the material in these dishes soon turned toward 

 the direction from which the air was coming, walked down over 

 the edge of the dish, on to the bottom of the large dish, and toward 

 the point where the air current struck the bottom, usually stop- 

 ping two or three centimeters from the center; here they would 

 remain, with their axes parallel to the direction of the air current, 

 and their heads facing to windward for half an hour or longer, 

 if not disturbed. They appeared to be pressed down against 

 the bottom of the dish by the force of the air current, quivering 

 slightly with variations in the pressure, and they were observed 

 not to be feeding. New comers, alighting in any other than the 

 position above described, moved about in short jerks, until they 

 had assumed this position. Sometimes chains of two or three, 

 immediately back of one another, would be formed, with spaces 



73 



