CACTUS SOLUTION AS AN ADHESIVE. 



11 



in the mortality. The plants used were both sugar beets. The result 

 of this experiment shows that by the use of cactus the lasting qualities 

 of the poison on the plants may be greatly increased. 



The spraying in experiment No. 24 was done at the same time as in 

 experiment No. 22, 1 pound of zinc arsenite being used to 64 gallons 

 of water but only one-third of a pound of cactus to each gallon, the 

 glutinous matter having been extracted by soaking the cactus for four 

 days in water. Salicylic acid was added as a preservative. The 

 sugar beet was sprayed on April 15, and on April 16 five beetles were 

 placed on the plant. April 17 one beetle was found dead and four 

 still feeding. April 18 three had died from the effect of the poison 

 and two were yet feeding. On April 20 all were dead. During the 

 four days the beetles were encaged they appeared to feed very rap- 

 idly, as they had been confined for several days without food. This 

 proves that 1 pound of powdered zinc arsenite with cactus to make it 

 adhere is more effective than 2 pounds in the paste form and just as 

 effective as 3 pounds in the paste form. 



The plant in experiment No. 25 was sprayed with 1 pound of zinc 

 arsenite to 35 gallons of water and at the same time as No. 23, on 

 April 11, with the same quantity of cactus, but the beetles were not 

 placed on the plant for six days after spraying. On April 17 three 

 beetles were encaged, and by the 22d all were dead. 



On April 5, after spraying a field plat of cabbage with ferrous 

 arsenate, several plants were treated in the insectary. The strength 

 used was 1 pound to 12 gallons of water. One pound of cactus was 

 used to each gallon of water, the cactus water having been made 26 

 days when used. It was prepared on March 16 and sodium benzoate 

 added as a preservative. On April 11 six beetles were placed on a 

 cabbage plant covered by a lantern globe. Table XV gives the 

 number of beetles that succumbed in a given period. 



Table XV. — Experiment No. 26. — Cactus as an adhesive with ferrous arsenate, 



Brownsville, Tex., 1914 . 



Date. 



Beetles 

 present. 



Living. 



Dead. 



Feeding. 



6 



6 







4 



6 



6 







5 



6 



6 







5 



6 



6 







1 



6 



3 



3 



2 



5 



1 



4 



1 



5 



1 



4 



1 



5 







5 







Not feed- 

 ing. 



Apr. 13. 

 Apr. 14. 

 Apr. 15. 

 Apr. 16. 

 Apr. 17. 

 Apr. 18. 

 Apr. 20. 

 Apr. 21. 



The beetles from some cause fed very sparingly the whole time they 

 were encaged. Whether the poison was distasteful or the plant had 

 become tough, could not be ascertained. 



