8 ROYAL SOCIETY OF CANADA 
attacks of injurious insects are met. All remedies are devised with 
regard to the nature or habits of the insects to be controlled. Insects 
can be divided into two large classes by the nature of their mouth parts: 
(1) Mandibulata, or Biting insects, and (2) Haustellata, or Sucking insects: 
The first of these can be destroyed by placing active poisons on their 
food-plants, so diluted as to be innoxious to the plant, but at the same 
time sufficiently powerful to destroy the insects. For the second class, 
insecticides which kill by mere contact with their bodies, are necessary. 
We have now standard active remedies which answer for both of these 
classes, and, in addition, many preventive measures may be taken by 
which injury is warded off. All these methods, together with the neces- 
sary apparatus, have been treated of with considerable detail in Bulletin 
11 of the Central Experimental Farm series, copies of which are still 
available for all who apply for them; and [ now propose, under a few 
heads, to speak as briefly as possible of some instances of good entomo- 
logical work which demonstrate the practical value of a knowledge of 
economic entomology. 
CONTROLLING BY REMEDIES. 
Reverting now to the two classes of injurious insects—Biting insects 
and Sucking insects,—I will draw your attention to the value of the two 
standard remedies for these classes: 1. Paris green, which is an arsenite 
of copper containing about sixty per cent of arsenic, is almost an ideal 
material for the purposes to which it is applied by entomologists. Its 
characteristic green colour advertizes its poisonous nature, and prevents 
many accidents which might arise from carelessness ; its insolubility in 
water and under most conditions to which it is likely to be exposed 
before it is applied, renders its use very simple. Its fine state of division 
makes its dilution, either with liquids or dry powders, very convenient. 
Moreover, its extreme virulence as a poison makes it possible to dilute it 
very much indeed without destroying its efficacy as an insecticide. The 
recent discovery that the admixture of an equal weight of fresh lime 
with the arsenite neutralizes its caustic effect upon vegetation, has 
removed the last drawback to the use of this material. This has also 
simplitied immensely the question of the most suitable remedy for Mandi- 
bulate insects. Now, a standard strength of one pound of Paris green, 
one pound of quick-lime and two hundred gallons of water, may be 
recommended for use on all kinds of vegetation. Three years ago I had 
the honour of laying before this section some of the remarkably satis- 
factory results which had been obtained by spraying fruit-trees with 
Paris green to protect them against insect injury. Since that time I have 
lost no opportunity to bring this matter officially before the farmers of 
Canada, and to-day there is more spraying being done throughout the. 
