ENTOMOLOGY. (JUl 



plasmolyzes the protoplasm, and that this plasmolysis is in direct ratio 

 to the solubility and quantity of the compound employed. The burning 

 point of barium arsenate is stated to be reached when it is used at the 

 rate of 20 lbs. to 150 gal. water; that is, upon oak and apple. Larvae 

 in the second, third, and fourth molt, it is stated, are killed within 5 

 days when sprayed with this compound in the proportion of 3, 1, and 5 

 lbs. to 100 gal. water; while larvae in the fifth molt require 10 to 20 lbs. 



The barium arsenate is obtained by precipitating arsenate of soda 

 with a soluble barium salt, such as barium chlorid. 



Comparative tests with new and old arsenicals on foliage and with larval, 

 V. L. Marlatt (pp. 30-35). — Paris green, pulverized Paris green, Scheele's 

 green, London purple, and arsenite of lead, both with and without an 

 admixture of lime were employed. The first 3 were used in strengths 

 of 1:100; 1:100; 1:80; andl:53&. The London purple and a mix- 

 ture of equal parts of Scheele's green and arsenite of lead were employed 

 at the rate of 1:160 and 1:100. No injury resulted. But in another 

 series of tests made on peach, apple, and cherry, in which the poisons 

 were used at the rate of 1 : 100, some damage was done, as shown by the 

 following table : 



Injurious effects of Paris green, Scheele's green, and London purple. 



Poison. 



Apple. Cherry. Cotton. 



Paris green, ordinary 



i leaves lost . . Very alight spot- No injury No injur j whatever. 



ting. 



Injury slight — I»i>. 



insignificant. 



....do Do. 



....do Do. 



Paris green. pulverized-! } leaves lost .. All more or less 



spotted. 



Scheele's green J leaves lost do 



London purple Allleaveslost. Much scalded, in- 

 cluding edges. 



The effect of arsenicals seems to be to hasten the ripening of the 

 leaves and perhaps also of the fruit. 



In experiments on larva, no noticeable difference between the poisons 

 was found when used at the rate of 1: 80. Used at the rate of 1:100, 

 they gave somewhat unsatisfactory results. When used at the rate of 

 1:100, Paris green and Scheele's green show but little difference, either 

 when used alone or with lime. London purple and arsenite of lead are 

 much slower in their action. 



The number of grains of active poisonous principle held in solution 

 in each gallon of mixture when the latter is made in the proportion of 

 1 :100 is stated to be as follows : Ordinary Paris green, 0.87 ; pulverized 

 Paris green, 1.18; Scheele's green, 2.50; London purple, 7.93: arsenite 

 of lead, 0.91. 



Summarizing all his experiments, the author states that Scheele's 

 green and arsenite of lead are to be preferred to any of the others. 



On the futility of trunk and crown washing against the elm leaf beetle, 

 L. O. Howard (pp. 36-38).— It is concluded that fully 70 per cent of the 

 insects drop from the limbs and that this demonstrates the superiority 

 of spraying over other methods of combating this insect. 



