THE BEAN LADYBIRD. 17 



left these plants at once. Larvae hatching from eggs deposited before 

 the application of the poison were also killed where they fed on 

 spraj^ed leaves. The older larvae;, however, appeared to die of star- 

 vation rather than from eating the poisoned foliage. 1 



ARSENITE OF ZINC. 



Experiments were made with powdered arsenite of zinc at the 

 rate of 1 pound to 20, 30, 40, and 60 gallons of water, respectively. 

 The burning effect on the foliage was in all cases less than where 

 arsenate of lead or Paris green was applied, and usually a larger 

 proportion of the insects was killed. The burning was most ap- 

 parent about the margins of the holes made in the leaves by the in- 

 sects in feeding. Many larvae died after eating the poisoned foli- 

 age, but, as with the other arsenicals, the effect on the beetles was 

 uncertain. All factors considered, the most promising results were 

 obtained with zinc arsenite at a strength of 1 to 40. This caused 

 comparatively slight burning and killed an appreciable number of 

 the insects. It should not be overlooked, however, that the killing 

 of the beetles is uncertain and that the burning effect on the plants 

 will vary greatly with their age and tenderness. It is probable that 

 Mexican beans, with relatively tougher foliage, would show less 

 injury from burning than the more tender-leaved string beans 

 treated in these experiments. Zinc arsenite in experiments con- 

 ducted in New Mexico by Merrill at the rate of 2 pounds to 50 

 gallons of water produced practically the same results as powdered 



lead arsenate. 



PARIS GREEN. 



Experiments were made with Paris green at the rate of 1 pound 

 to 60 and to 80 gallons of water. As a result of these tests the 

 beans were destroyed by burning due to the presence of free arsenic. 

 Most of the larvae were killed, but many of the beetles escaped. In 

 the face of these results, Paris green at these strengths can not be 

 recommended as a means of controlling the bean ladybird. Every- 

 one who has tried Paris green has experienced the same failure. 

 Sodium arsenite is at least equally dangerous. 



SUMMARY OF SPRAYING EXPERIMENTS. 



The experience of entomologists in spraying with arsenicals in 

 Colorado and New Mexico tends to show that arsenate of lead acts 

 largely as a repellent rather than as an insecticide, which is true 

 also of its effectiveness in the case of such other pests as the striped 

 cucumber beetle. 



Bordeaux mixture, which has come to be considered a standard re- 

 pellent against flea-beetles, should be tested against the bean lady- 

 bird in the future. 



1 Powdered lead arsenate at the rate of 5 pounds to 50 gallons of water was no more 

 effective but did no damage to the plants in experiments made. It should not he used at 

 this strength. 



