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CAPT. J. DAVIDSON. 



the light through the narrow slit (s) into the cage. It is necessary to have the slit 

 only just wide enough for flies to get through. The writer remembers the afternoon 

 this specimen trap was made. It was eagerly set with an attractive bait of 

 vinegar, sugar and bread, and after three hours an enormous number of flies 

 were imprisoned. They dashed about hither and thither in the cage, making a 

 frantic buzzing noise. In the evening the cage was put into my bell-tent and after 

 sundown the flies quietened down, although they were actively crawling about 

 the walls of the cage. During the night I was awakened by something crawling over 

 my face and on lighting the candle, was disgusted to find the roof of my tent literally 

 black with flies. About 75 per cent, of my prisoners had escaped, owing to the 

 too generous width of the slit (s). 



The flies in the cage can be destroyed by fumigation with pyrethrum powder, or 

 cresol heated on a tin. The smell which remains about the cage after fumigation 

 tends to keep the flies away, so they were allowed to pass from the cage into a bag 

 made with mosquito netting, and were then fumigated. 



(4). Poisoned bait.— The use of the poisoned bait method was carried out with 

 success under mobile desert conditions. Formalin (3 per cent, solution) sweetened 

 with sugar was used in mess-tents, but sodium arsenite (Na 2 HAsO s ) was used in 

 the form of poisoned bait. Pieces of old sacking were soaked in a mixture of 1 per 

 cent, solution of sodium arsenite in water containing 20 per cent, of ghur, and 12 per 

 cent, of glycerine, rolled into a ball and hung near latrines. The glycerine prevented 

 rapid drying. 



Fig. 7. Tobacco tin containing poison 

 solution (s), with wicks (w) made of 

 teased tent-rope passing through the lid. 



As previously described, sodium arsenite was used at the manure dumps. 

 Owing to rapid evaporation spraying on exposed surfaces was found not to be 

 satisfactory. 



The sodium arsenite-ghur poisoned bait, devised originally by Dr. Berlese and 

 used with success in Mesopotamia by Professor Lefroy, gave excellent results. A 

 sweet syrupy mixture was made containing 1 per cent, sodium arsenite, ghur and 

 glycerine. This was put into cigarette tins or other available shallow tins. The 

 lid of the tin was pierced with a number of holes, through which pieces of teased 

 tent rope were drawn, forming a number of wicks (fig. 7). When the lid was replaced, 

 these dipped into the mixture in the tin and sucked it up, so that the rose-like top 



