28 The European Elm Scale 



Mixture 12 1-2 per cent Kerosene. Counted 200 ; dead, 101 ; living, 

 99 ; per cent dead, 50.5 ; per cent living, 49.5. 



Mixture 10 per cent Kerosene. Counted 250; dead, 116; living, 

 134; per cent dead, 46.4; per cent living, 53.6. 



KEROSENE EMULSION, LOT II 



(With Atomizer in the Open Air) 



Reno, January 30th, 1908. 



Material — Hibernating larvae more or less concealed in craclts 

 in the bark of limbs of American Elm. The limbs chosen were of 

 various sizes, but an efEort was made to secure material for each test 

 which would be of about the same character. The limbs were so sep- 

 arated from each other as to prevent the mixture used in one test 

 from falling on the limb to be used in another. In general the mate- 

 rial represented fairly thejisual position of the hibernating larvae. 

 As the trees were badly infested, most of the trees contained great 

 numbers of larvae. 



Conditions — A clear, sunny afternoon with a brisk wind from the 

 iv'est. The applications were made between 1:30 and 3:00 P. M., 

 when the thermometer stood at about forty degrees. 



Application — Each sample was blown on the bark in a .fine 

 spray with an atomizer of a usual pattern. In each instance it soon 

 wet the bark so thoroughly that every sprayed crack was full of the 

 solution, which filled the cracks and stood on the bark in drops like 

 milk. A strong effort was made to have the work with the atomizer 

 represent a thorough job of spraying, in which the bark should be wet 

 to a dripping condition. With the earlier and weaker samples, evap- 

 oration was so rapid that the emulsion soon dried on the bark leaving 

 no trace of its use except a clean and somewhat oily appearance of 

 the bark. The cracks chosen were all on the underside of the limb. 

 They were filled as full of the emulsion as they would hold. 



Sprayed January 30th ; examined March 3d, 1908. 



Test for Death — As the weather since the spraying was 

 warm and dry the larvae had ample time to dry and shrink after their 

 death and before examination. This made the test for death an easy 

 one to apply. Those larvae which were shrunken and blackened and 

 motionless were counted as dead; the remainder as living. Each 

 larva was inverted with the point of a dissecting needle and the ven- 

 tral surface examined in a strong light. The room temperature stood 

 at 65 degrees during the examination and the motion on the part of 



