THE CAMPHOR THRIPS. 27 
On October 20. 1921, four lots of 10 eggs each, deposited the same 
day. were fumigated with hydrocyanic-acid gas, two oilier lot- being 
kept as check-. The four lots were placed in an airtight fumiga- 
torium with a capacity of 25 cubic feet and subjected for two hours to a 
charge of gas produced from materials used at the strength of 1 ounce 
of sodium cyanid, 2 ounces of sulphuric acid, and 4 ounces of water to 
100 cubic feet of space. After fumigation the limbs eontaining the 
eggs were removed and placed with the cheeks in the laboratory. The 
following day no effects could be noted on the eggs. On Oetober 27. or 
seven days after treatment, the eggs were still unchanged and the check 
eggs were hatching. On October 28 all the checks had hatched. The 
experiment was discontinued October 31. sinee none of the fumigated 
eggs had hatched. Xo change in their appearanee could be seen, but 
when broken they were found to contain a watery fluid, with no evi- 
dence of an embryo. 
A similar experiment was performed on October 21. using 1 ounce 
of sodium cyanid and an exposure of one hour. The results were 
similar, no eggs having hatched up to October 31. 
On November 1 another lot of eggs were fumigated, using one-half 
ounce of sodium cyanid to 100 cubic feet of space and an exposm 
one hour. The checks all hatched on November 9 and 10. Xone of 
the treated eggs hatched, a few appearing shrunken and dried out after 
several days, but most of them remaining unchanged in appearance 
and containing a watery fluid. A final experiment was made on 
November 1. using two lots of eggs of about 40 each, which were 
fumigated for one hour at the rate of 1 ounce of sodium cyanid to 
100 cubic feet of space. On November 7 a few of the eggs were 
shrunken and collapsed. By November 12 all the checks had hatched 
but none of the treated eggs hatched, nor did they contain any live 
embryos. 
In all these experiments there was 100 per cent mortality of the 
eggs. Not a single egg remained alive after the fumigation. Results 
from the various dosages and exposures used did not differ appre- 
ciably. A strength of one-half ounce of sodium cyanid killed the eggs 
as well as stronger dosages. For commercial practice, however, it is 
recommended that the trees be exposed for one hour in an airtight 
fumigatorium to gas produced at a strength of 1 ounce of sodium 
cyanid to 100 cubic feet of space. The experiments prove that 
nursery stock can be entirely freed from the camphor thrips in all 
stages by this treatment. 
Further experiments with living nursery stock showed that the 
trees will stand this treatment without any serious damage. On cut 
limbs the bark turned black after a few days and dried out sooner 
than it normally would, but on living camphor trees which were 
defoliated and well pruned back there was no apparent deleterious 
effect. In fact some of them withstood a dosage of 2 ounces of 
cyanid and an exposure of two hours. 
Fumigation of course would not be practicable on commercial 
camphor plantations, nor would it be possible to use it on large 
ornamental trees and hedges. It is recommended only for nursery 
stock or small trees when removed from the ground for transplanting. 
