at « 
ae 
170 Proceedings of the Royal Physical Society.” 
from the egg to the shoot apex. With this object in view trees were 
sprayed with Paris green, lead arsenate, and lead chromate shortly before 
the hatching of the eggs was expected, and also after the first caterpillars 
had emerged. The results are given in the tables. ; 
2. Treatment that might kill the young larve in the first or second instar, 
that is, while they are feeding on the outer leaves of the bud, and before 
they have begun to spin to any great extent.. With this object in view a 
nicotine spray was used with very good results, as shown in the table. 
Based on the observation that a great number of such young larve had been: 
drowned during a day of incessant rain, heavy syringing with water from a 
garden hose was also tried. This gives the best results if the day chosen for 
the treatment be one when the humidity of the atmosphere is sufficient to ' 
prevent the speedy drying of the leaves. On a bright day it is almost 
useless. 
SUMMARY OF RESULTS OF INSECTICIDE SPRAYS. 
The following is a general summary of the results of the various 
insecticides used, with regard to— 
1. The Mortality of the Larve due to the Spray. 
In control trees, on an average, about 85 per cent. of the buds become 
infested. 
In trees treated, as described, with lead arsenate about 55 per cent. 
became infested. | 
In trees treated with lead chromate about 75 per cent. 
Trees sprayed with Paris green showed no diminution of the : 
percentage of buds infested. This must be ascribed partly to 
weather conditions unfavourable to the experiments. . 
In trees treated, as described, with nicotine an average of about 
10 per cent. of the buds remained infested with living cater- . 
pillars. 
2, The Hffect of the Spray on the Foliage. 
None of the insecticides used proved in the least detrimental to the 
health of the trees. The thin milky-white coating left by spray- 
ing with lead arsenate gave to the trees the bluish tint of a 
eucalyptus, and as this coating is not readily washed off by 
rain, the appearance of the trees was thus affected for several 
months. 
The lead chromate spray is apt to make yellow patches on the 
leaves where a precipitate settles, giving them a “ variegated ” 
appearance, which is, however, not very noticeable. 
