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SOME FLY POISONS FOR OUTDOOR AND HOSPITAL USE. 



By A. C. Jackson and H. M. Lefroy, 

 Imperial College of Science and Technology, South Kensington. 



The method of poisoning flies by the exposure of solutions of sodium arsenite 

 and sugar is one that has been advocated by entomologists in Italv and in 

 South Africa for some years, and yielded good results in Mesopotamia in 1916 ; 

 for in hot cUmates, where flies come readily to sugar solutions, the use of an 

 outdoor poison is specially valuable. But there are obvious disadvantages in 

 using any arsenic solutions ; for not only are they poisonous in themselves, but 

 the disposal of residues is not easy, as the arsenic and sugar remain poisonous if 

 thrown away, or if they dry on sand or soil. It would thus be useful to substitute 

 for arsenic some compound less poisonous to man and less stable in a soluble 

 form when thrown away. 



The only generally known poison besides arsenic is formaldedyde, which is 

 •excessively variable in action and too volatile for outdoor use in a hot climate. 

 There are many formulae for its use indoors, varying usually from about 1 to 4 

 per cent, of the formaldehyde. Phelps has recently suggested sodium salicylate 

 (U.S. Public Health Reports, Washington, D.C., xxxi, 1916, pp. 3033-3055) as 

 an indoor poison, and this seems suitable for outdoor use also. There have been 

 other suggestions, such as quassia, bichromate, pepper, etc. ; and Morrill has 

 tested and reported on a number of other substances (Jl. Econ. Entom., vii, 1914, 

 p. 268). This matter was tested by Miss Lodge on Musca dmnestica in 1915, and 

 details of her experiments were pubUshed (Proc. Zool. Soc. London, 1916, 

 pp. 481-518). She tried a considerable range of compounds and found potassium 

 iodate a hopeful substance. In 1916 Miss Lodge did further work, particularlv 

 Avith sodium iodate and formaldehyde. With the former she killed from 90 to 99 

 per cent, of flies in the morning after offering the poison, i.e., within 18 hours, and 

 the flies fed on the bait readily. She tried other sodium and potassium compounds, 

 but no very definite decision was reached. An account of these experiments will 

 be pubhshed shortly, with her other work, and Miss Lodge has kindly allowed us 

 to quote her results. 



In 1917, having the experience in Mesopotamia with sodium arsenite as a basis, 

 the writers made further trials with fly poisons. The substances were tested 

 (with 20 per cent, sugar solutions) usually at a strength of 2 per cent, by weight ; 

 they were offered to flies in confinement in large glass cylinders with gauze covers, 

 and anything abnormal was noted. The results obtained are by no means decisive ; 

 but as they may be useful to others who may be engaged in testing possible poisons, 

 we have decided to record them. It is convenient to class the compounds in three 

 divisions : — 



(1) Those that kill quickly ; 



(2) Those that kill on the second day ; and 



(3) Those that seem to be harmless at the strength tested (2 per cent.). 

 (C357) B 



