Eudemis nevana, Hb., the Holly Tortrix Moth. 171 
Paris green, in the strength employed, did not alter the appearance 
of the foliage. 
The nicotine spray cleansed the trees of other insects as well as the 
caterpillars. After spraying, these trees were freer from spiders 
and aphides than neighbouring control trees. 
3. The Ultimate Effect on the Tree. 
At the end of the season, trees successfully treated by the nicotine 
spray were distinguished by the marked superiority of the 
growth of their shoots, and by the absence of ragged and dis- 
torted leaves. Those trees which had been sprayed with lead 
arsenate and lead chromate showed comparatively little superiority 
over untreated trees, and in this respect were less distinguishable 
from controls except by the traces of the spray. 
The insecticides used may therefore be arranged in order of their 
efficiency, as follows :— 
(1) Nicotine. (3) Lead chromate. 
(2) Lead arsenate. (4) Paris green. 
In order to test the effect of hydrocyanic acid gas on the eggs, three 
different fumigation experiments were made. 
Experiment 1.—On 23rd February a young holly, 18 inches high (in a 
large pot of soil), with a number of eggs here and there on its leaves, was 
placed in a fumigation chamber, and exposed for an hour to hydrocyanic 
gas fumes. The proportions of cyanide of potassium, sulphuric acid, and 
water used in the experiments were— 
Potassium cyanide 1 part by weight 
Sulphuric acid . , 1 part . 
Water . of parts 5, 
and the amount of space per unit of cyanide was at the rate of 1 oz. of 
cyanide 98 per cent. purity per 300 cubic feet of space. In Experiment 1, 
‘egos removed after fumigation and examined microscopically were found to 
be uninjured, and the development of others left on the leaves of the plant 
progressed normally. 
Lzpervment 2.—The same holly was—with the eggs in a more advanced 
stage of development—again exposed to an hour’s fumigation with hydro- 
cyanic acid gas. The gas was of the same strength as in Experiment 1, and 
the eggs held embryos that had reached a distinct caterpillar form, but the 
caterpillars were still surrounded by a thin layer of yolk. The plant after 
fumigation was placed out in the garden, and observations made. The eggs 
without exception hatched in due course. 
