
CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF 
THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 
COLLEGE. E. L. MARK, DigECTOR. NO 162. 
THE REACTIONS OF THE POMACE FLY (DROS- 
OPHILA AMPELOPHILA LOEW) TO LIGHT, 
GRAVITY, AND MECHANICAL 
STIMULATION. 
FREDERIC W. CARPENTER. 
THE observations which this paper records were made on the 
movements of the common pomace or little fruit fly, Drosophila 
ampelophila Loew. Insects of this species can be collected in 
abundance in the autumn, and a culture can easily be maintained 
in the laboratory all winter if it is kept supplied with decaying 
fruit such as bananas or apples. The eggs are laid in this 
material, which later is used by the larvae as food. ; 
When a large cylindrical glass vessel containing a stock cul- 
ture of these flies was placed on a table near a window, it was 
noticed that the flies accumulated in the greatest numbers on 
the upper part of the side of the vessel nearest the window. 
This indicated that they were positively phototropic to ordinary 
daylight, and probably negatively geotropic, although it seemed 
possible that their position near the top of the vessel might have 
been due to the fact that, owing to its position near the bottom 
of the window, the vessel was illuminated more brightly above 
than below. It was also observed that when the vessel was 
exposed to direct sunlight the flies, after a time, tended to 
accumulate, not on the surfaces toward or away from the win- 
dow, but in intermediate positions on the two sides. Here the 
majority remained quiet in the regions of least illumination. A 
similar observation was made by Loeb (’93) on planarians, which 
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