SCALE-INSECTS. 35 
23. Tobacco. A good remedy against Jarve and adults; 
doubtful against the eggs. Fumigation has no effect 
on scale-insects, except sometimes on Dactylopide, 
or “mealy bugs” (Hubbard; Comstock; Personal 
experiment). The tobacco should be -applied in a 
pretty strong solution; but the expense in this 
country would be probably too great for general use. 
24. Whale-oil and whale-oil soap have been already alluded 
to under the head “ Kerosene.” hey are both useful 
ingredients in mixture with that substance, if pro- 
curable cheaply. , 
From the foregoing list it will be gathered that, if experi- 
ment, combined with knowledge of the habits and life-history of 
scale-insects, can be relied on, there is no substance better 
adapted for their destruction than kerosene, mixed with oil, or 
milk, or soap solution, and carefully applied. It has been 
already observed that the killmg of the eggs is absolutely 
necessary for thorough clearing-away of the insects; and, to 
quote again the words of Mr. Hubbard, kerosene is “ almost 
the only substance which will with certaimty lull the eggs with- 
out at the same time destroying the plant.” 
But precautions must not be neglected. Persons who reck- 
lessly use any remedy, or who apply it too thickly or in too 
strong proportions, must expect their trees to suffer. Nor 
must the weather and the time of the year be overlooked. 
Winter is the best season for all remedies ; and, preferably, cool 
and cloudy days. Again, if substances soluble m water, such 
as potash or soda lye, soap solutions, &c., be employed, it must 
be expected that a day’s rain will wash a good deal of them off, 
and greatly reduce their efficacy. These are things which many 
people forget; they fancy that because somebody has cleared 
his trees with, say, castor-oil in winter they can do the same 
thing in full heat of summer; or, because a lye solution has 
done well in the dry climate of California, that it will be 
equally good in the rains of New Zealand. Still more is it a 
fallacy to imagine that rule-of-thumb methods, not founded upon 
any knowledge of the nature, habits, and life-history of the 
insects, are likely to be really efficacious. 
Little need be said here of a remedy which has had, to some 
extent, the authority of Professor Riley, and which is recom- 
mended by Mr. Howard (Report U.S. Dep. of Agric. 1880-81, 
