FUMIGATION AGAINST NIK PURPLE SCALE. 
41 
Bcope of the schedule, the Limits were made verj broad. Prom the 
difference in strength of killing dosage between these three experi- 
ments we would be able to determine the effect of length of exposure 
on results secured. 
To obviate as much a> possible the leakage of gas, \\ bich w ould vary 
iu trees of different sizes, trees were chosen of as uniform a Bize as 
could be obtained. The cubic contents of the trees chosen for the 
first two experiments did not vary greatly and the tree- ranged 
between 11 and 14 feet in height. As in the first two experiments 
most of the larger trees had been used, for the third experiment we 
were' compelled to utilize those remaining, which varied somewhat 
in size, and were also, for the most part, noticeably -mallei' than 
those represented in the 4 lirst two experiments. 
During the latter part oi January an examination was made of the 
result- of these experiments. Fully two weeks were devoted to this, 
and thousands of the purple scale were scrutinized. The method 
employed was a very careful one. In each case the scales were 
overturned ami examined with a powerful hand lens. In those 
instances in which the entire contents of the scale were not at once 
revealed, the delicate ventral scale was ruptured and the contents 
scraped out. Through this method not a single egg could escape 
observation. 
Four trees were used in each test and an examination to deter- 
mine results was made of each. This examination included many 
infested leaves and branches taken as close to the ground as possible 
and up to 6 or 7 feet above the ground. Infested fruit was also 
examined when obtainable. The average condition existing in these 
four trees was taken to indicate the result of the test. 
The chemicals were used in the following proportion: Potassium 
cyanid, 1 part: sulphuric acid. 1 part: water, 3 parts. 
Table IV. — Fumigation for tfu purple scale, experiment X<>.. 
[Length of exposure, thirty minutes; height of trees, ll to 14 feet.] 
Number < >" ani ' 1 
.\umn.r per 100 
treated. „ 
i in leaves and 
branches. 
on fruit. 
[nsects 
alive, 
approxi- 
mately. 
Eggs 
normal. 
approxi- 
mately. 
[nsi cts 
ili\ e, 
approxi- 
mately. 
normal, approximately. 
Ouncfi. 
4 
4 1 
i 11 
4 
1 
1 
1 2} 
I'i r n ill . 
II 


n 


" 
Per a nt. 
Over 75. 
MlMllI 7.".. 
i • than i. 
ii 
(i 
n 
Per a nt. 
10 
2 




(1 
1) 
Fully 'in percent. 
Many normal eggs found under ever] 
scale containing eggs. 
Some normal eggs found under almost 
evi ry scale containing eggs. 
15 per cent. 
5 7 pi r cent. 
i per cent. 
Two instances of ippari ntly normal eggs. 
None. 
