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THE EFFECT OF VARIOUS CHEMICALS 

 ON BLOW-FLY. 



By W. F. COOPER, B.A. (Cantab.), F.C.S. and W. A. B. WALLING. 



(From the Cooper Laboratory for Economic Research, Watford.) 



Introduction. 



The experiments described in the present communication were made 

 with the object of determining the insecticidal effect of various chemicals, 

 a large number of which, hitherto, have never been actually employed 

 as insecticides 1 . Most of these chemicals are already articles of com- 

 merce, whilst the remainder, if they should prove to be effective, could 

 be produced on a commercial scale, if the demand arose. 



The selection of the chemicals used was purely haphazard, the 

 immediate object being to eliminate the least promising, and to gain 

 such insight as would lead to a later and more precise series of experi- 

 ments with the more promising compounds ; also the range of selection 

 was as wide as possible, and this has been justified by the results, as 

 some of the most efficient compounds were unusual ones. 



The choice of a suitable pest on which to work was also a matter 

 for some consideration, especially as it was desired that the preliminary 

 investigation should have as high a practical value as possible. 



Some time ago, the authors were investigating the effects of different 

 chemical reagents upon the eggs of Lepidoptera, but, for various reasons, 

 they were forced to the conclusion that ova are unsuitable subjects for 

 experiments of this nature, and the work was abandoned. These 

 objections do not apply to the larva, and the question resolved itself 



1 Since this paper was written, the almost universal state of war has created conditions 

 which are unprecedented in their possibilities for the propagation of disease by flies. In 

 thoso areas which are at present the scene of military operations, the problem of dealing 

 with flics, as agents in the transmission of disease, is likely to become acute in the immediate 

 future; and we venture to hope that our results, incomplete as they arc may possibly 

 afford some useful suggestions to those who arc undertaking an active campaign againsl 

 this menace. 



