REMEDIES AGAINST FOREST INSECTS. 31 
poultry have access to it; or, if still partly adhering, it may be ripped from the wood 
by barking tools and burnt; but it is a tangible and serious cause of injury, and if 
our landed proprietors were fully aware of the mischief thus caused to their own trees 
and those of the neighborhood they would quickly get rid of it. 
INSECTICIDES AND MEANS OF APPLYING THEM TO SHADE AND FOREST 
TREES.* 
This subject may be divided into two parts, viz, (1) a discussion of 
insecticides and (2) a discussion of insecticide apparatus. 
(1) insecticides. — Remedial measures against forest-tree insects 
are not different from those employed against the insect enemies of fruit- 
trees or farm and garden crops. The same species are frequently the 
culprits in both cases ; and, in general, insects of the same orders and 
families, having similar habits and requiring similar treatment, attack 
wild-growing, woody plants aud the cultivated sorts. 
For convenience of treatment, the first part may be considered under 
the following heads : Insecticides which act through the food ; insecti- 
cides which act by contact; fumigants and gases. 
Insecticides which act through the food. — These insecticides 
are available against all mandibulate insects that feed externally on the 
leaves, such as the larvae of Lepidoptera, larvae and adults of leaf- 
feeding beetles, and saw-fly larvae. Gall-insects, leaf-miners, and in- 
sects which burrow beneath the bark or in the wood cannot be con- 
trolled by these means. 
It would be possible to enumerate under this heading a large number 
of substances depending for their effects on arsenic, strychnine, or other 
poisons, but I prefer to limit the discussion to the consideration of two 
substances which are now commonly used to the exclusion of nearly all 
others. 
Paris green and London purple. — The arsenites of copper and cal- 
cium, Paris green and London purple, are so well known as not to 
need particular description here. The safety and efficiency with which 
they can be used and their slight cost fully satisfy all the demands 
of practical work. 
As containing records of a general nature, together with full in- 
structions for the use of these poisons, I can not do better than quote 
from Bulletin No. 10 of the division of entomology,! the conclusions 
being based on experiments under my direction, especially by the late 
Dr. W. S. Barnard. 
The quotation refers particularly to work against the imported Elm 
leaf- beetle (Galeruca xanthomelama) and deals with the treatment of 
elm trees only, but the results obtained may apply to other insects 
infesting various shade and forest trees. The recommendation given 
• 'Prepared, at the author's request, by Professor Riley. 
t Our Shade Trees and Their Insect Defoliators, by C. V. Riley, Entomologist, 
Washington, 1887. Second revised edition, 1888. 
