CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE MUSEUM OF 

 COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. E. L. Mark, Director. No. 191. 



THE REACTIONS OF THE POMACE FLY, DROSO- 

 PHH.A AMPELOPHILA LOEW, TO ODOROUS 

 SUBSTANCES 



WILLIAM MORTON BARROWS 



With Five Figures 



I Introduction 515 



II Experiments c 1 6 



1 Preliminary experiments 516 



2 Experiments with alcohol, acetic acid and acetic ether 519 



3 Experiments on the directive effects of odorous substances 527 



4 Experiments to determine :he position and function of the olfactory sense organs 530 



III Theoretic discussion 535 



IV Summary 536 



V Bibliography 537 



I INTRODUCTION 



Drosophila ampelophila is a small fly about three millimeters 

 in length belonging to the family Drosophilidae. It lays its eggs 

 on fermenting fruit, which serves as food for both the larvae and 

 the adults. The ease with which large numbers of these insects 

 can be reared in the laboratory during the winter as well as the 

 summer, and the definiteness with which they react to many forms 

 of stimuli, make them favorable subjects for experimentation. 

 Since they find their food with great certainty even in the dark, a 

 habit that seemed to involve the sense of smell, I was led to take 

 up an investigation of their reactions to odorous substances. 



Where the flies were abundant, it was noticed that they often 

 entered bottles and other receptacles containing alcohol. The 

 fact that the fermenting fruit upon which they feed is continually 

 generating alcohols and other related compounds, led me to sus- 

 pect that it was these substances that served to attract the flies, and 

 that they therefore probably presented a clear case of chemotro- 

 pism among air-inhabiting animals. 



The Journal of Experimental Zoology, vol. iv, no. 4. 



