The European Elm Scale 29 



the living larvae was usually prompt; in some instances, however, 

 motion was stimulated by the near approach of a hot dissecting needle. 



Sources of Error — The larvae were no longer wholly dormant; 

 for many of the males had begun their cocoons. Before beginning 

 their cocoons the males often wander about on the limb and settle in 

 new situations. I do not think that in the present instance this habit 

 had progressed far enough to cause any important error. A second 

 source of error lies in the fact that some of the dead larvae may have 

 become detached from the branch by wind or rain and so lost to the 

 count. The crowded condition of the dead larvae in the cracks, to- 

 gether with their protected situation on the underside of the limb 

 makes this source of error seem unimportant. 



Result op Count — Mixture 16 2-3 per cent Kerosene. Counted 

 1109 ; dead, 912 ; living, 197 ; per cent dead, 82.2 ; per cent living, 17.7. 



Mixture 12 1-2 per cent Kerosene. Counted 723 ; dead, 350 ; living, 

 373 ; per cent dead, 48.4 ; per cent living, 51.6. 



SCALECIDE 



This is an insecticide which in appearance and action closely 

 resembles the Kerosene Emulsion. Its base, however, is a heavier oil 

 than kerosene, and it seems far more effective as an insecticide. The 

 Scalecide used was part of a ten-gallon sample sent out for trial by 

 the manufacturers. As it had been standing for some time, the sample 

 in the original can was first stirred thoroughly with a stick, the can 

 itself was then rocked back and forth violently for several minutes 

 in order that the small amount, about one pint, which was drawn off, 

 might fairly represent the contents of the can. The small sample was 

 then mixed with water in the proportions indicated in the accounts 

 of the experiments which follow. The tree chosen for the experiments 

 represented natural conditions of temperature and the other climatic 

 factors; for it stands in the open air in the midst of the infested dis- 

 trict on Mill Street, Reno, Nevada. In each of the following atomizer 

 experiments the larvae were first examined with a magnifier to see 

 that their appearance was wholly normal, and in every instance the 

 bark was examined to ascertain whether or not it was sound. Much 

 care was exercised to prevent the possibility of the spray used in one 

 test touching the bark which had already been sprayed or which was 

 to be sprayed in another test. These atomizer experiments should give 

 a good idea of the efficiency of the sample of Scalecide used, under the 

 conditions named. 



