EXAMINATIONS OF THE SCALE INSECTS. 15 
EXAMINATIONS OF THE SCALE INSECTS. 
After fumigation, the fruit was kept in an outbuilding on the 
Agricultural Department grounds, the temperature varying mostly 
between 30° and 40° F., being rarely higher than 45° F. In 1906-7 
the fumigated fruit for examination as to condition of scales was 
taken direct from this storehouse; but in 1907-8 it was first held for 
a couple of days in a warm room, which induced a prompt discolora- 
tion of the dead scales, greatly facilitating their recognition. The 
plan was to make two examinations of the scales on each lot of fruit 
fumigated: The first two weeks, and the second four weeks, after the 
time of fumigation, and this in the main was adhered to. All ex- 
aminations of scales were made by aid of a dissecting microscope, and. 
a dissecting needle was used to remove the scale proper, exposing the 
body of the insect. The color of the body was relied upon to de- 
termine if the insect were dead or alive, and there was not often 
difficulty in thus definitely classifymg them. In some cases, ex- 
amination of doubtful specimens was made under a compound 
microscope to detect possible body movements, and a method of 
staining was used to a limited extent. In all cases, specimens doubt- 
fully dead were regarded as alive, and, as will be noted in the tabu- 
lated results for 1906-7, these doubtful cases were numerous. 
In 1907-8, however, the expedient of warming the fruit for a 
couple of days before each examination always resulted in the prompt 
discoloration of the scales, leaving no doubt as to their condition. In 
view of the uniformly successful results in killing the scales in all 
experiments made in 1907-8, and many of them duplicates of those 
made in 1906-7, it is considered practically certain that the insects 
regarded as alive in 1906-7 were in reality dead, but not showing 
sufficient discoloration for positive recognition on account of the 
comparatively low temperature at which they were held. 
The supply of infested fruit for fumigation was kept in the original 
barrels in a local cold-storage plant, being taken out shortly before 
needed, the time depending upon the nature of the test to be made. 
Thus in treatment of fruit in a dry condition it was necessary to 
remove it several days in advance, so that the moisture condensing 
on the cold fruit would dry. In the fumigation of fruit in a moist con- 
dition, however, the condensed moisture on the cold fruit immediately 
after coming from cold storage put this in the desired condition for 
experiment. 
An important question in the employment of hydrocyanic-acid 
gas in the destruction of scale insects on apples was the possibility of 
injury to the fruit. In this matter the Bureau of Entomology had 
the expert aid of Mr. William A. Taylor, pomologist, of the Bureau of 
Plant Industry, and his associates, who are also responsible for the 
correctness of names of varieties. There is also the question of 
89165—Bull. 84—09——_3 
