THE IMPORTED ELM LEAF-BEETLE. 15 



pies 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 cooL 

 of the tree on the northwest side during the morning- is too unhealthy 

 for the favorable development of the larvae or of the eggs deposited 

 there ; but whether this be true or not, the insect probably prefei 

 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 larva? 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, JJlmus 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. 



XT, 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.camj)estris, U.suberosa, U.effusa,niK\ U.parvifolia xiberica). 

 The last named is not attacked as much as the American. The young 

 larva' 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 25, in 18S3, this species was completely eaten and 

 brown in our grove, at which date the U. montana examples retained 

 more than half their verdure ; in some individuals nearly all ; and the 

 common American elm was perfectly green. The V. 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 Bpecies ^\' elms. 



Effects of arsenical Poisons on Insect and Plant. — Species o\' elins 

 somewhat differently affected by the poison. When treated alike there 

 is always manifest some difference in the susceptibility o\' different elms 

 to the corrosive effects of the poison. Even individuals of the same 



