R. A. Wardle 5 



It would appear too that Lucilia prefers carrion in bulk and is 

 primarily a fly infesting carcases in the open, thus not having the 

 economic significance of CaUiphora as regards foodstuffs. 



The hygrometric condition of the atmosphere is not without signifi- 

 cance. In continuously fine dry weather, oviposition occurred more 

 frequently in the early morning between dawn and 8 a.m., whilst the 

 atmosphere was somewhat moist. A sunny morning following a wet 

 night, or a sunny afternoon following a wet morning, were particularly 

 favourable. 



Wind was antagonistic. Few flies were on the wing and the baits 

 became dry and unattractive. 



Experiments in prevention. 



Screening and trapping, as already pointed out, are not methods 

 readily applicable to the problem in hand. Attention was therefore 

 directed to the question of repellent substances. 



These fall into two classes: 



(1) Substances directly appUcable to foodstuffs. 



(2) Substances indirectly applicable to foodstuffs. 



The range of repellent substances that can be directly apphed is 

 Hmited. A trial was made with the household remedies usually recom- 

 mended against flyblow, such as vinegar, onion juice, pepper, salt, 

 tomato juice, etc., and the Ust was extended by the addition of formahn, 

 boracic acid, and a proprietary article termed Milton, having a slight 

 chlorine odour. Slices of raw kidney or liver were sprayed with or dipped 

 in solutions of these substances and exposed, one batch in the sunshine, 

 one batch in the shade. The results obtained from the baits exposed in 

 the sunshine were of little use as even the controls were rarely blown. 

 Flies fed freely on all the samples but particularly on those treated with 

 vinegar, weak Milton, and borax. The samples treated with concentrated 

 Milton and with 2^ per cent, formalin were avoided when flies were few, 

 when the number of flies increased these samples were attacked also. 



The following table is typical of the oviposition results observed in 

 twenty repetitions of the experiment. 



The weak solution of Milton would appear to be more repellent than 

 the strong but other experiments did not confirm this. In fact, weak 

 Milton and vinegar seemed slightly attractive. The success of pepper 

 appears due to the drying effect produced upon the surface of the bait. 

 It was not so effective when apphed to Uver or to very juicy meat. Pre- 

 cipitated chalk gave similar results. Cooper and Waning(3), experi- 



