R. A. Wardlp: 7 



The second class of repellent substances, namely such as are indirectly 

 applicable to meat commodities, comprises such substances as have a 

 distinct and penetrating odour, the essential oils, phenols, paraffins, 

 esters, etc. For example, the following list of substances was found by 

 Miss Lodge to be decidedly repellent; pipendine, oenanthol, xylol, amyl 

 acetate, methyl salicylate, anisole, citral (strong), ethyl sulphocyanide, oil 

 of thyme, of cassia, of Java citronella, of p)alma rosa, of bay, of heliotrope, 

 of lavender, of cinnamon leaf, of cinnamon bark, of sassafras, of cloves, of 

 camphor. 



Cooper and Walling give: methyl salicylate, p-nitraniline, picric acid, 

 creosote, green oil, boracic acid, mustard oil, sod oil, iodoform, di-methylani- 

 line, quinoline, allyl alcohol, fusel oil, pine oil, alizarine oil, origanum oil, 

 sinapis oil, alloin, saponin, copper carbonate, nitrobenzene, aniseed oil. 



Now a substance may be repellent to a fly attracted to the bait 

 from motives of curiosity or hunger, without being necessarily repellent 

 to a female fly under the far stronger oviposition-impulse. Many of the 

 substances listed above are, further, obviously unsuitable for use in 

 proximity to foodstuffs, and others are too expensive or difficult to 

 procure for the average food vendor. 



A selection of substances was made therefore, and, as in practice it 

 would be undesirable to apply them directly to foodstuffs, an indirect 

 method of testing them was adopted. The food samples were placed 

 within cylindrical glass dishes over the opening of which a piece of cotton 

 twine netting was tied, after being smeared with the substance to be 

 tested. The netting was of quarter-inch diamond mesh, wide enough to 

 allow the largest Calliphora to slip in and out of the dish; as the dishes 

 were of glass, equal illumination of both sides of the netting was obtained 

 and the possibihty of the mesh acting as a mechanical obstacle to the 

 ingress of the flies thus excluded. It has been asserted by Spence(i) that 

 flies can be prevented from entering a room through open doors and 

 windows by covering these openings with wide-mesh netting, even 

 herring netting, provided there is no source of illumination behind the 

 door or window. In my later experiments, however, a box of three feet 

 cubic dimensions, lined with black cloth and completely closed except 

 for a narrow slit, was readily entered by large numbers of Calliphora, 

 and was also entered quite easily when one side was removed and re- 

 placed by black netting. 



To perfume the netting, it was found quite sufficient to moisten the 

 palms of the hands and to roll the netting between them. Substances 

 selected were the more easily obtainable essential oils — cloves, citronella, 



