34 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
effective against thfl Insect, but that this- poison injures the plant more than does the 
London pniple. 
Three-fonrthfl <»t'a ponnd of Paris greeo to ■ ban.] :;r, of 10 gallons) of water, with 
:> quarts of flour, may be regarded ss ■ poison mixture «>t" medium or average strength 
fol treating elms against these beetles, and tin- indications thue l'ar are that the 
amount of Pai is green should not be inereased above one pound or he diminished much 
below one-hall a pound in this mixture. To a bucketful of water three-fourths 
ounce of Paris green may be used. The action of this poison is Blow but severe, and 
varies much with the weather. Thus far the results of fcOSte have been varied no much 
by the weather and different modes of preparation and application that they will be 
repeated. When u>ed strong enough to cauterize the leaves the poisonous action 
upon the plant may be observed to continue for several TTTttdre 
The species of Limits are quite susceptible to the effects of poison, 
perhaps as much so as any common species of forest tree. But little 
can be added to the above quotation, as there are few experiments re- 
corded concerning work of this kind on other forest trees. With fruit 
trees and vines there is a large experience, and the results indicate 
That either of these arsenicals can be safely used on the most tender 
plants in proportion of 1 pound to 100 gallons of water, if properly 
atomized. Strong, hardy plants readily stand a strength of 1 pound 
to 50 gallons of water, if applied with proper care. It is safe to con- 
clude that between these two limits a strength suitable for all plants 
may be obtained. 
A thoroughly atomized weak mixture will, under favorable con- 
ditions, prove as efficient as the stronger ones ; but in wet, showery- 
weather weak applications are more liable to be washed off. 
Properly atomizing the liquid is of the greatest importance, for only 
by this means can all the foliage be reached. The even distribution 
thus obtained enables the leaves to retain a greater amount of the 
poison with less injury than when sprayed in coarse drops. 
Insecticides which act by contact. — This class of remedies 
apply principally to non-masticating insects, i. e., those which take 
their food through a sucking-tube or proboscis, such as the plant- 
bugs, aphids, and scale insects. They may. however, often be suc- 
cessfully applied to soft-bodied maudibulate insects, in lieu of the 
poisonous mixtures. 
There are a great variety of substances, such as alkaline washes 
and powders, and preparations of oils, and particularly the products of 
petroleum, which have been successfully used on insects affecting 
roots, trunks, branches, and foliage of trees. The experimental data 
concerning them have been mostly obtained from cultivated fruit trees 
and vines, but they will prove equally available against the similar 
enemies of forest trees. 
Wood Ashes and Lime. — Of alkaline powders, wood ashes aud slaked 
lime are commonly used either pure or in mixtures around the bases of 
trees or interred in the earth among the roots of plants to destroy root 
aphids or other insects affecting the roots. Xo definite instructions 
concerning their use can be given, as both substances vary as to strength, 
