THE IMPORTED ELM LEAF-BEETLE. 
former have more delicate foliage, lighter in cold]' and weight, appar- 
ently less succulent. 
Certain elms of the specie s U. campestris and other species which 
overpoisoned, and shed most of their leaves in consequence in the last 
of June, 1883, sent out a profuse new growth of leaves and twigs. 
foliage fell gradually for three weeks, and this was somewhat prom 
by the succeeding rains. 
The larva' move from place to place so seldom that if' tin- leaves 
imperfectly poisoned from the mixture being weakly diluted, or from its 
application only in large, scattered drops, which are much avoided by 
the larva*, they are not killed off thoroughly for several days, and in all 
cases it requires considerable time to attain the full effect of the poison. 
This result appears on the plant and on the insect. After each rain 
the poison takes a new effect upon the plant and the pest, which indi- 
cates that the poison is absorbed more, or is more active when wet, and 
that it acts by dehydrating thereafter. Where the tree is too strongly 
poisoned, each rain causes a new lot of leaves to become discolora 
the poison or to fall. On some of the trees the discoloration appears in 
brown, dead blotches on the foliage, chiefly about the gnawed places 
and margins, while in other instances many of the leaves turn .yellow. 
and others fall without change of color. The latter may not all drop 
from the effects of poison, but the coloration referred to is without doubt 
generally from the caustic action. The poison not only produces the 
local effects from contact action on the parts touched by it, but follow- 
ing this there appears a mere general effect, manifest in that all tie- fo- 
liage appears to lose, to some extent, its freshness and vitality. This 
secondary influence is probably from poisoning of the sap in a moderate 
degree. When this is once observable, no leaf-eater thrives upon the 
foliage. Slight overpoisoning Seems to have a tonic or invigorating 
effect on the tree. 
Preventive Effects of the Poison. — In this grove the elms that were 
soned in 1882 were attacked in the spring of L883 less severely than 9 
those which were not poisoned the previous year. This would seem to 
imply that the insects deposit mostly on the trees nearest to where they 
develop, and are only partially migratory before ovipositing. Tin 
tack afterward became increased, probably by immigration and the 
new generation, so that later in the season the trees were mostly in- 
fested to the usual extent. 
In the region of Washington a preventive application of poison should 
be made before the last of May or first of June, when the eggs an 
ing deposited and before they hatch. This will prevent the worms from 
ever getting a start. By the preventive method the tree escapes two 
kinds of injury : first, thai directly from the eating by the insect; second, 
that which follows indirectly from tin 4 deleterious effects of the pd i 
on the plant, for its caustic effect is much greater where the lea\ es 
been so gnawed that the poison comes in contact with the sap. 
