14 



JOUENAL OF AGRICULTURE OF P. R. 



Experiment XVI. 



Five hundred beetles were caught while feeding on the foliage 

 of young cane. They were placed in a cage and fed for ten days 

 on a common weed, "bleda," {Amaranthus spp., a favorite food 

 plant of the beetles), the foliage of which had been sprayed with 

 a solution of arsenate of lead three pounds to fifty gallons of water. 

 At the end of this time the cage was examined and four hundred 

 iind sixty-eight of the beetles were found dead while tlie remain- 

 ing thirty-two were very sluggish. An analysis of the dead beetles 

 revealed traces of arsenic. 



Experiment XVII. 



A patch of "bleda*' in the vicinity of some cane fields was sprayed 

 Avith a solution of ai*senate of lead of the same strength as that used 

 in tlie previous experiment. At night five hundred and sixty-five 

 beetles were caught feeding (m this poisoned "bleda" and were im- 

 mediately placed in a cage and fed on fresh, unsprayed materia!. 

 At the end of a week one hundred and fifteen were found dead, ami 

 i\ week later two hundred more. Analysis shoAved traces of arsenic. 



Experiment XVIII. 



This experiment was a repetition of Experiment No. XVI, with 

 the diiference that a solution of Paris green was used to poison the 

 ^' bleda" in place of the arsenate of lead. The solution was made 

 up of one pound Paris green, one hundred and twenty-five gallons 

 of water, twelve and one-half i)ounds of flour and two and one-half 

 gallons of milk of lime. At the end of ten days an examination re- 

 vealed two hundred and nineteen dead beetles, two hundred and 

 eighty-one still being alive. 



Favorite food plants of the beetles in the fields were sprayed 

 with different strengths of arsenate of lead and Pai'is gi'een. Beetles 

 were collected at night feeding on these sprayed plants and wei'e 

 kept in cages without food to Wiitt-li the effect of the poison on them. 



Camiarina fiiuiiieHfoHa. 



" fSrlirniilia iinrtriyiri'iixix. 



