330 



A. C. JACKSON AND H. M. LEFROY. 



and '5%, which also proved an effective fly poison. The iodates however are less 

 soluble than the fluorides and much more expensive. We obtained the following 

 figures : — 



Ammonium and potassium. 3 : 5 ortho-dinitro-cresylate (5%, 2% and 1%) gave 

 encouraging results, but a further series of experiments proved that these 

 substances, at the above strengths, render the food or solution distasteful to flies, 

 which only feed upon it when forced to do so by hunger. This was borne out by 

 the few deaths recorded at the first count ; while at the second count most or all 

 of the flies had succumbed. 



Ammonium 3 : 5 para-dinitro-cresylafe did not give such good results as the 

 ortho-dinitro-cresylate. 



Sodium, and potassium salicylates (2% and 1%) will poison flies, but they appear 

 to act more slowly and fail to kill at weaker strengths, such as '5%, and therefore 



are only to be recommended when fluorides and iodates are unobtainable, 

 gave the following figures : — • 



They 



Fed to flies. 



2% Sodium sahcylate 



2% Potass'm sahcylate 



1% Sodium salicylate 



1% Potass'm salicylate 



2.15 p.m. 



2.30 p.m. 



2.15 p.m. 



12 a.m. 



No. of 

 FUes. 



148 

 27 

 123 

 29 



No. dead at 

 5 p.m. same day. 



No. dead at 

 10 a.m. next day. 



98 

 25 

 83 

 17 



Class II. 



Magnesium per-borate, approximately at 2% strength (the substance was rather 

 insoluble), killed 36 out of 66 flies at the second count (10 a.m. next morning). 



Copper sulphate (5%) killed 50% of the flies by 10 a.m. the next morning. 



Ciqyrol (2%) in food mixture accounted for 65% on the morning of the third 

 day. 



Cadmium sulphate (5%) poisoned 8 flies out of 66 by 5 p.m. of the first day 

 (experiment started 10 a.m.), and at 10 a.m. next morning 46 in all were de-ad : 

 a 2% strength poisoned 1 out of 16 on the evening of the first day, and by next 



