THE CAMPHOR THRIPS. 23 
to he practically as many adults and larva' present as on the un- 
sprayed checks and no dead insects were found. On June 21, which 
was r bright, warm day, several adult thrips wore found in the space 
of a very few minutes. They continued to feed on the young shoots 
and the spray apparently did them little or no harm. It was very 
obvious that this spray, without the lime-sulphur solution, was 
not satisfactory. It was much less effective than when the lime- 
sulphur solution was added. 
Several experiments were also conducted to determine the effect 
of the lime-sulphur, tobacco, and soap combination spray upon 
the camphor thrips eggs. On August 23 twenty-three eggs which 
had been deposited August 22 and 23 were dipped in some of the 
solution which had been used for spraying the camphor trees. On 
August 27 no eggs had hatched. Two days later the eggs still had 
not hatched, but appeared to be in perfect condition. The checks 
at this time were hatching. On August 30 all the treated eggs were 
broken and found to be dried out or to contain a partly developed 
embryo. All of the eggs were dead. Again on August 31 a limb 
containing camphor thrips eggs of various ages was dipped in the 
same solution. Some of these eggs were hatching on the day they 
were treated. September 1 two eggs hatched and each of the larva? 
was found dead near the eggshell from which it had emerged. On 
September 2 no eggs hatched. From September 3 to 5 a few eggs 
hatched and the larvae were found crawling on the limbs. Of the 
eggs present on August 31 only a small percentage hatched. The 
dipping tests certainly indicate that practically all eggs which are 
wet by the spray will fail to hatch. The check eggs all hatched in 
the normal time. Where the main object is to kill the eggs, it 
would be advisable to make the solution somewhat stronger than 
that used in these tests. 
Several experiments were conducted in dusting infested camphor 
trees with lead arsenate, calcium arsenate, flour of sulphur, flowers 
of sulphur, dry lime-sulphur, and Bordeaux powder. These dusts 
were used both, separately and in various combinations with each 
other and with lime, but in all cases positive killing effects were 
lacking. Dusts containing nicotine sulphate were not available at 
the time. 
PRUNING. 
Under the system of pruning as practiced on semicommercial 
plantations, in which the growth was cut back without regard to the 
location of the nodes, or the trees were dehorned at a height of from 
4 to 6 feet (PL IV, B ; PL VI, A) , the pruning not only was injurious to 
the trees but stimulated their growth so that they were not resistant 
to cold. This method also seemed to produce an unlimited food 
supply for camphor thrips, and following such pruning they appeared 
in countless numbers. It was obvious that a different system of 
pruning must be adopted which would avoid not only the direct injury 
to the camphor trees but also the secondary damage caused by the 
thrips. 
The method consists of cutting off the trees at the level of the 
ground. This eliminates the dying back of the cut ends due to 
branch pruning, avoids the injury which might follow low tempera- 
tures, and destroys the food supply and breeding places of ihe earn- 
