THE IMPORTED ELM LEAF-BEETLE. 15 
ples far more markedly than upon others. This one-sidedness is espe- 
cially apparent in the trees which were the most severely eaten. Some 
trees show the southeast side completely devoured, but the northwest 
side only half consumed and comparatively green. Such are average 
cases. 
The inferences have been, that the shade, dampness, and coolness 
of the tree on the northwest side during the morning is too unhealthy 
for the favorable development of the larve or of the eggs deposited 
there; but whether this be true or not, the insect probably prefers to 
deposit chiefly in the middle of the forenoon, and on that part of the 
tree which is then warmest. This would give a greater number of the 
eggs at the outset on the southeast side, as observation seems to con- 
firm, and since the young larve do not migrate to any noteworthy ex- 
tent, the one-sidedness described would result, whether the northwest 
side were unhealthy or not. The former explanation is most probably 
the correct one, as we have noticed that the insect is less injurious dur- 
ing very wet summers. : 
Preferences of the Elm-beetles for certain Varieties and Species of Elms.— 
The American Slippery Elm does not occur in this grove, but only one 
native species, the common American Elm, Ulmus americana. This is. 
practically free from the ravages of the beetle, on which account it may 
be preferred to the European species. It is tall, and has gracefully 
arched branches, making it as ornamental as any European kind, yet 
as a Shade tree it does not equal the U. montana of the Old World. The 
latter has a broader, denser crown, but the attack on it is considerable, 
enough to leave the choice in favor of the American species. 
U. montana seems the best European species grown here for shade, 
since the other foreign elms here cultivated are not dense enough. This 
applies to U. campestris, U.suberosa, U. effusa, and U. parvifolia (siberica). 
The last named is not attacked as much as the American. The young 
larve cannot develop on it, but die quite soon, without growing, and 
they gnaw the leaves very little. The other foreign species mentioned 
are seriously eaten; the severest attack being upon the U. campestris, 
the favorite food of this insect. 
As early as June 20, in 1883, this species was completely eaten and 
brown in our grove, at which date the U. montana examples retained 
_ nore than half their verdure ; in some individuals nearly all; and the 
common American eim was perfectly green. The U. campestris is one 
of the poorest elms for shade, and its total abolishment throughout the: 
entire country would probably lessen the assault on U. montana to a. 
comparatively unobjectionable extent. This measure should be insti- 
tuted against the pest, and for the sake of the other species of elms. 
Effects of arsenical Poisons on Insect and Plant.—Species of elms are 
somewhat differently affected by the poison. When treated alike there 
is always manifest some difference in the susceptibility of different elms. 
to the corrosive effects of the poison. Even individuals of the same. 
