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application of such researches lies in the possibility that, in some 
instances, they may be utilised in their preparation of lures to entice 
the females, in virtue of their chemotropic properties, to deposit their 
eggs thereon. Such eggs could then be readily destroyed. If devices 
of this nature were in existence, methods of combating the larvae after- 
damage had already been committed would no longer be necessary. 
Hewlett (1912, p. 412) has also conducted some experiments in India 
with the fruit fly, Dacus zonatus. He selected a number of essential 
oils and found that citronella oil was remarkably attractive to that 
species. He furthermore noted that only males were attracted. He 
mentions that in less than half an hour a handkerchief, moistened with 
this oil and exposed in a peach orchard, became almost hidden by the 
multitude of the insects attracted thereto. As the reaction was 
confined to the male sex, and did not in any way appear connected 
with feeding habits, he formulated the hypothesis that the odour of 
citronella oil resembled that emitted by the females to guide the males 
to them. Devvitz ascertained that it is the odour of the nectaries of 
the vine flowers that attracts the vine moths and induces them to 
oviposit on the unopened buds. Labergerie (1911, p. 612) conducted 
a series of experiments with molasses diluted with water, and exposed 
in a vineyard in 3000 earthen vessels and 200 metal ones. By this 
method, between the 18th of May and loth of September, there resulted 
the capture of 290,000 vine moths and their larvae at small expense. 
Barrows (1907, p. 515) has made a study of the chemotropic reactions 
of the pomace fly. Drosophila ampelophila. This insect occurs in great 
numbers around cider-presses, packing sheds and orchards, when fer¬ 
menting fruit is present; within the latter it deposits its eggs and its 
larvae develop. He studied the reactions of the fly to various substances 
occurring in fermenting fruit. Ethyl alcohol, acetic ether, and acetic and 
lactic acids were experimented with separately and in mixture. The 
insect was found to be attracted in the most marked degree by a 
mixture of ethyl alcohol of 20 “/o strength and acetic acid of 5'’/o- If 
was further discovered that cider vinegar and fermented cider contain 
alcohol and acetic acid in percentages very close to those just quoted. 
A series of experiments were conducted proving that the fly discovers 
its food by means of the olfactory sense and this sense is located in 
the terminal joint of the insect’s antenna. 
These instances have been enumerated with the object of pointing 
out what an abundant field exists for physiological research as regards 
chemotropism. It is a line of work that is likely to ultimately achieve 
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