68 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



for eight days. Lead arsenate precipitated from tenth molar solutions 

 of lead nitrate and disodium arsenate was m.ore readily eaten by the 

 Japanese beetle than ordinary commercial lead arsenate. This lead 

 arsenate consisted of about 25 to 30 per cent, basic lead arsenate and the 

 balance acid lead arsenate. Reducing the amount of lead arsenate 

 from 2 lbs. to 1 lb. per 50 gallons increased the amount of feeding on the 

 sprayed foliage, but the am.ount eaten was not sufficient to cause death. 

 Freshly prepared ferric hydroxide mixed with lead arsenate, thereby 

 decreasing its toxicity, increased the feeding. Aluminimi hydroxide, 

 which would not be as effective an antidote, when mixed with lead 

 arsenate only slightly increased the feeding of the beetle on the sprayed 

 foliage. Lime or lead carbonate, which also decreases the toxicity of 

 lead arsenate by converting som^e of it to basic lead arsenate, increased 

 the feeding in cage experiments. By using gelatin to coat the particles 

 of the lead arsenate its action was delayed and an increased amount of 

 sprayed foliage was eaten by the beetle. From these observations the 

 conclusion was reached that the beetles were repelled either by the 

 taste of the arsenical or by its toxic effects. 



It would appear unlikely that the taste of the arsenical causes the 

 beetles to leave the sprayed plants. If such is the case, then the taste 

 of the arsenical depends upon its toxicity, since the beetles will readily 

 eat arsenicals low in toxicity. Powdered burned alum or quinine were 

 eaten, compounds which are surely far from tasteless. One striking 

 experiment showed that the taste of the arsenical probably did not 

 influence the results. Twenty beetles consumed in six days; all the 

 foliage of a smartweed sprayed with the strychnine sulphate at the 

 rate of 2 pounds to 50 gallons. Not a single death resulted. Twenty 

 beetles in six days ate very little of the foliage of a smartweed sprayed 

 with strychnine arsenate at the rate of 2 pounds to 50 gallons, but six 

 of the beetles died. It would require a very discriminating taste to 

 distinguish between strychnine sulphate and strychnine arsenate. 



Arsenic is classed as an irritant poison. Almost the first symptoms 

 in higher anim.als are vomiting and profuse and painful diarrhea. The 

 withdrawal of water from the body results in thirst and a dryness of the 

 mouth and throat, m.aking swallowing difficult^ 



To what an extent these symptoms are developed in the Japanese 

 beetle is unknown, but beetles which have consumed a killing dose or 

 close to a killing dose of arsenic suffer from diarrhea. Should the 

 reaction in the beetle to arsenic poisoning be similar to that in higher 

 animals, pain would be a prominent symptom. A compound which 



iSollman Torald— A Manual of Pharmacology — 1917, p. 739. 



