; 
29 
tion of the insecticide, and also to the softening and loosening of the 
scale itself, enabling subsequent weather conditions of moisture and 
cold to be more fatal. 
With such biting insects as caterpillars and slug worms after treat- 
ment with arsenicals or other poisons death rapidly follows, the time 
being somewhat in proportion to the size of the larvee and their natural 
vigor. Soft-bodied larve, such as the slug worms and very young 
larvee of moths and beetles or other insects, are killed in a day or two. 
Large and strong larvee sometimes survive the effect of poison for eight 
or ten days, and leaf-feeding beetles will often fly away and perish from 
the poison in their places of concealment. 
Many larve or other forms of leaf-feeding insects, after taking one 
or two meals of poisoned foliage, will remain in a semitorpid and dis- 
eased condition on the plants for several days before they finally sue- 
cumb. The protection to the plant, however, is just as great as though 
they had died immediately, but misapprehension may often arise and 
the poison may be deemed to have been of no service. 
The complete extermination of insects on plants is often a very diffi- 
cult, if not an impossible, undertaking. This is especially true of scale 
insects. In California even, where the work against these enemies of 
fruits has been most thorough and successful, experience has shown 
that the best that can be done is a practical elimination of the scale for 
the time being, and it is often necessary to repeat the treatment every 
year or two. In exceptional cases once in three years suffices. With 
leaf-feeding insects it is often possible to effect complete extermination 
with the use of arsenical poisons. Such sucking insects as plant-lice 
may also be completely exterminated. But in general all applications 
or methods of treatment must be recognized, more or less, as a con- 
tinuous charge on the crop, as much so as are the ordinary cultural 
operations. 
CONTROL OF INSECTS BY CULTURAL METHODS. 
It is much easier to ward off an attack of insects or to make condi- 
tions unfavorable for their multiplication than to destroy them after 
they are once in possession; and in controlling them, methods and sys- 
tems of farm and orchard culture have long been recognized as of the 
greatest value, more so even than the employment of insecticides, 
which, in most cases, can only stop an injury already begun. Insects 
thrive on neglect, multiply best in land seldom or never cultivated, 
and winter over in rubbish, prunings, or the undisturbed soil about 
their food plants, and become, under these conditions, more numerous 
every year. It is a fact of common observation that it is the neglected 
farm, vineyard, or orchard filled with weeds or wild growth which is cer- 
tain to be stocked with all the principal insect enemies; and, on the 
other hand, thorough and constant culture, with the removal and burn- 
ing of prunings, stubble, and other waste, the collection and destruce- 
tion of fallen and diseased fruit, and the practice, where possible, 
