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must, then, become familiar not only with the adult insects but 
study their life-history and habits. 
We have spoken of the mouth-parts of insects. Knowledge of 
the manner in which insects feed will enable us to determine by 
the injury to the plant the insect responsible for the damage 
whether biting or sucking, and the nature of the remedy to be 
applied. 
Time will not permit a discussion of particular insects or details 
as to remedies. We are dealing with the subject in a general way. 
insect suppression or control may be classified as follows : Direct 
measures, including the use of insecticides, or any measure that 
actually by mechanical means reduces the numbers of the insect ; 
and the preventive measures, including cultural methods, natural 
enemies, quarantine and sanitation. 
In direct efforts of control dependence is placed in the main 
upon insecticides, that is, insect killing substances. Insecticides 
may be classed under two general heads, namely, substances for 
killing biting insects, and substances for killing sucking insects. 
The insecticides used for biting insects are termed "stomach 
poisons." Those used against sucking insects consist of "contact 
poisons," "external irritants" and "poisonous gases." 
Insects that bite off and swallow the portions of plants upon 
which they feed would likewise take into their systems any poison 
that might be placed upon the surface. Therefore, in combating 
an insect belonging to this class, that is, those actually chewing 
or gnawing into the foliage, the idea is to cover the surface with 
a poison, harmless to the plant, but sufficient in strength to kill the 
insect when taken into the stomach. The insect killing substance, 
or insecticide as it is called, is applied evenly over the surface in 
the form of a fine spray or powder by various machines made 
expressly for the purpose. The arsenical poisons are the common 
remedy for the biting insects and among the various compounds, 
Paris green has been the standard one. Paris green is usually 
applied in milk of lime. The lime in the mixture has the property 
of off-setting the burning qualities of the Paris green. In low 
grade Paris green there is a large excess of free or water soluble 
arsenious oxide which will have a direct injurious effect on the 
foliage of the plant and give it the appearance of having been 
burned. The Paris green to be harmless to the plant should be 
practically insoluble in water. The finely divided crystals are only 
in suspension in the spraying mixture and for this reason, con- 
stant agitation of the liquid is necessary during the process of 
spraying. These crystals, though insoluble in water, are soluble 
in the digestive juices of the intestines of the insect and thus death 
is brought about by an absorption of the poison. One of the more 
recent arsenical poisons is seemingly better suited to the Hawaiian 
conditions than Paris green. This compound is an arsenate of 
lead. Paris green, as has been said, is quite likely to burn the 
foliage, especially if it is of low grade or is not used with lime; 
