The European Elm Scale 2/ 



somewhat promptly. As a result, a few of the more active larvae had 

 begun to wander about on the table over which the branch was sus- 

 pended and a few undoubtedly escaped. This would render the per- 

 centage of deaths due to spraying a little too high, probably a trifling 

 error in this instance. The contrast between the temperature of the 

 solution and that of the room was a matter of no importance in the 

 present instance, as the emulsion was atomized by a current of air. 

 Tests by the thermometer with a room temperature of sixty degrees 

 and a solution temperature of one hundred showed that when the bulb 

 of the thermometer is sprayed with the atomizer under the conditions 

 named the mercury does not rise more than a degree or two. This is 

 not true with the large spray pump, however, for when water whose 

 temperature stood at 130 degrees was sprayed on the bulb in a room 

 whose temperature was 50 degrees the mercury rose to 80. The 

 mechanism of the spray pump is entirely different from that of the 

 atomizer; for in the former a column of air is not used to atomize the 

 solution, but the fine spray is formed by discharging the water under 

 high pressure with a rotary motion from a small aperature. 



RESULTS, KEROSENE EMULSION, LOT I 



Test for Death — Material examined in the laboratory at a room 

 temperature of 80 degrees, under the dissecting microscope, by the 

 strong diffused daylight of a north window. Scales of the normal, 

 clear purple-brown color, not shrunken, with body fluids not thickened, 

 were counted as living if they moved legs or antennae when inverted 

 by the point of a dissecting needle. Those shrunken, blackened and 

 oily or deep purple in color, motionless, were counted as dead. With 

 the 16 2-3 per cent emulsion the test for death was easily applied. With 

 the weaker emulsions it was applied with increasing difficulty, as 

 many of the living were more or less shrunken and discolored and 

 their motion was exceedingly sluggish in many instances. It would 

 seem to me that better results would have been reached if the exami- 

 nation had been conducted at an interval of three weeks instead of a 

 single week. The conditions of the test, however, made this impos- 

 sible. There is a strong probability that some of those counted as liv- 

 ing would have been ranked among the dead at a later date. As very 

 few of the larvae were in any case thoroughly dry, I assume that very 

 few were dead at the time of spraying. 



Counts op Dead and Living — Note. Many of the "living" were 

 motionless until stimulated by the near approach of a hot needle. 



Mixture 16 2-3 per cent Kerosene. Counted 200 ; dead, 157 ; living, 

 43 ; per cent dead, 78.5 ; per cent living, 21.5. 



