February, '22] moore: Japanese beetle poisons 69 



would relieve the pain should increase the feeding of the beetle to a 

 point where it would be killed. Morphine sulphate would be the most 

 logical material to produce this result, but apparently it has no effect 

 since, when used at a concentration as high as 10 pounds to 50 gallons 

 of the spray, there was no marked improvement in the feeding of the 

 beetles. Atropine sulphate, chloral hydrate, aspirin, diethyl -b arbi- 

 turic acid, sodium bromide, lead bromide, and sodium salicylate, were 

 all tested without striking results. 



Attention was next directed to that group of substances class 3d as 

 intestinal sedatives. Bismuth subcarbonate is used on inflamed surfaces, 

 and as an intestinal sedative in cases of diarrhea. This substance was 

 tested in a cage experiment at the rate of 1 pound to 50 gallons of the 

 spray mixture containing 2 pounds of lead arsenate. One hundred 

 per cent, of the beetles were killed in 4 days compared with 12 — 14 

 days for lead arsenate alone. The action of bismuth subcarbonate 

 is not due to any specific effect of the metal but largely the mechanic 

 action of the compound in coating over the mucous membranes. The 

 basic salt of a cheaper metal might therefore be substituted for the 

 bismuth. Zinc subcarbonate gave fair results in cage experiments and 

 was then used in a field test. Beetles collected from the sprayed plants 

 one hour after spraying, and placed in a cage with an unsp rayed plant, 

 did not feed for 12 — 14 hours, showing that they had consumed nearly 

 a killing dose of the arsenical. 



Coating the particles of lead arsenate with some material which 

 would slow down its action was next tried. Lead arsenate coated with 

 lead oleate, lead stearate, zinc stearate, or lard gave good results in 

 cage experiments. It was necessary to use these materials as dusts 

 since it was difficult to "wet" the particles with water. A small area 

 of smartweed was thoroughly dusted in the field with lead arsenate 

 coated with lead stearate, and the beetles closely observed and collected 

 as they left the plants. At the end of two hours the beetles still present 

 on the plant were collected and the whole collection placed in a cage 

 with an unsprayed smartweed. Within 48 hours 86.2 per cent, of the 

 females and 61.5 per cent, of the males died. Later experiments 

 demonstrated that if the plants are very carefully dusted with lead 

 arsenate alone, that the beetles may be killed. The leaves of the 

 plants must be whitened with the pure lead arsenate by driving the dust 

 directly on the leaves. Lead arsenate or calcium arsenate allowed to 

 settle upon the foliage from a dust cloud will not result in a killing. 



These results show that to kill the beetle, one must have either a 

 large quantity of lead arsenate present on the foliage, or have the lead 

 arsenate coated in such manner that its action is delayed, so that in 

 the period of time elapsing between the first bite and the development 



