CACTUS SOLUTION AS AN/ ADHESIVE. 6 



make 20 pounds is comparatively small. The results of this spray- 

 ing operation were favorable, as the number of beetles present four 

 days later did not exceed 30 per cent of the original number, and a 

 majority of these had just arrived from near-by breeding quarters. 



In the next experiment 10 pounds of cactus were used in combina- 

 tion with 3 pounds of zinc arsenite and 50 gallons of water. As before, 

 the cactus was sliced and placed in water the evening previous to 

 spraying, and the following morning the solid particles were thrown 

 out before the poison was added. This spraying operation, with 

 but 10 pounds of cactus, gave good results, but the spreading quality 

 of the material was not as good as in the first experiment, in which 

 20 pounds of cactus were employed. 



In the next experiment, on April 3, 15 pounds of cactus were used 

 with 3 pounds of zinc arsenite and 50 gallons of water. In this 

 case the poison appeared to adhere and spread as well as when 20 

 pounds of the cactus were used. It thus appeared that 15 pounds 

 of the cactus with spines * would be, about the proper proportion to 

 use with 50 gallons of water in future work. 



The following table shows the mortality of Didbrotica balteata 

 placed on an encaged sugar-beet plant sprayed with zinc arsenite 

 at the rate of 3 pounds to 50 gallons of water plus 15 pounds of 

 prepared cactus: 



Table I. — Experiment No. 10. — Cactus as an adhesive in combination with 

 arsenite of sine, Brownsville, Tew., 1913. 



Date. 



Beetles 

 present. 



Living. 



Dead. 



Feeding. 



Not feed- 

 ing. 



Mar. 17 



5 

 5 

 5 

 . 5 

 5 



4 

 3 

 3 

 1 

 



1 

 2 

 2 

 4 

 5 



4 

 3 

 3 

 1 

 



1 



Mar. 18 



2 



Mar. 19 



2 



Mar. 21 



4 



Mar. 22 



5 







The beetles were placed on the sprayed plant at 6.30 p. m., March 

 15, but during several cool days which followed they were quite in- 

 active and probably fed but little. Cactus was tested in the insectary 

 as an adhesive before experiments were conducted in the iield, to 

 insure the absence of any inopportune chemical reaction that might 

 injure the plants. This experiment demonstrated that in approxi- 

 mately six days after spraying 99 per cent of the beetles succumbed 

 to the poison. Simultaneously with the foregoing experiment another 



1 Cactus with spines is preferable to the spineless varieties ; in fact, the spiny variety 

 appears to be nearly one-third richer in gluten. The Dairy Division of the Bureau of 

 Animal Industry has been conducting some cactus-feeding experiments for dairy cows the 

 past two years, and has made several analyses of both the spined and spineless varieties 

 of cactus. 



