THE REACTIONS OF DROSOPHILA AMPELOPHILA 



LOEW TO GRAVITY, CENTRIFUGATION, 



AND AIR CURRENTS 



WILLIAM H. COLE 



Contributions from the Zoological Laboratory of the Museum of Comparative 



Zoology at Harvard College 



No. 288 



INTRODUCTION 



Geotropism is characteristic of many animals and is often 

 closely correlated with equilibration. The ear in vertebrates 

 and the statocysts in invertebrates are evidently concerned with 

 this reaction. In insects, however, there are no semi-circular 

 canals or statocysts and it has not been proved that the so-called 

 " static " organs (chordotonal, etc.) have to do with geotropism. 

 Some other explanation is therefore to be sought. The experi- 

 ments here described were carried out with the common fruit- 

 fly, Drosophila ampelophila Loew, for the purpose of deter- 

 mining (1) whether or not it is negatively geotropic; (2) how it 

 responds to centrifugation and air currents; and (3) what mechan- 

 ism can control these responses. 



Carpenter ('05) concluded that gravity acted on Drosophila 

 as a ' directive ' stimulus only, some ' kinetic ' stimulation, 

 such as photic or mechanical, being necessary to induce loco- 

 motion. If this is true, how will Drosophila react to centrifugal 

 force and air currents under conditions where light and mechan- 

 ical stimuli are not effective ? This question was suggested by 

 the fact that the flies, without mechanical stimulation, were 

 found to respond negatively to gravity in the dark as well as 

 in the light. If it should be found that Drosophila reacts nega- 

 tively to centrifugation or to air currents, then it would seem 

 that gravity is a kinetic stimulus as well as a directive one. 

 Another question closely related with this one, which must be 

 considered is, by what means is the stimulus of gravity received? 



