14 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 
MORE RECENT EXPERIENCE AT THE DEPARTMENT. 
The more recent experience in the destruction of this Galeruca on the 
Department grounds may now be summed up, the experiments having 
been intrusted to Dr. Barnard. 
Past History of the Elms in question.— According to Mr. William Saund- 
ers, of this Department, these trees have been annually attacked by the 
European Elm Leaf-beetle since they were planted ten years ago, and 
about one year in three the injury has been severe, resulting in their 
-defoliation, while in other years, as in 1879 and 1880, there appeared 
comparatively none. In some seasons a second or autumnal set of leaves 
appeared after the trees had been stripped, and in certain of these in- 
stances the second crop of leaves became eaten; but in all cases he 
thinks the lives of the trees have not seemed to be endangered and they 
soon repaired the damage done. His belief is also that the pest did not 
become gradually worse and worse through the series of years during 
which it has been observed by him, still he regards the attack of 1882 
as worse than any known to him before on these trees or others, and 
he has noticed the effects of this insect since 1850, first in its earliest 
ravages about Baltimore, and later elsewhere. : 
Condition and Characteristics of the Grove in 1882 and 1883.— However 
it may be for the past history or future desirability of certain trees in 
the grove, in 1882 many exhibited various grades of feebleness, and some 
had dying branches. Indeed, a few of them had a very unhealthy as- 
pect the previous year also. Of course it can be claimed that their 
unhealthy condition is due to other causes than the insects; andit should 
be remembered that most are foreign species, each often represented in 
two or more of its varieties. Here all grow on level ground, whereas 
in a state of nature some belong to mountainous localities; others to 
the damp climate of England, &c. Therefore, many of them are grow- 
ing under abnormal conditions. They exhibit much variety in the 
relative abundance, size, form, and texture of the leaves. There is also 
great diversity in the density and form of branching. 
Extent of Injury in 1882 and 1883.—All] the varieties and species of 
elms in this grove, without exception, were preyed upon by the pest in 
1882 and 1883. The insect, however, showed decided preferences for 
certain individual trees, varieties, or species, stripping some completely 
before doing more than very slight harm to the leaves of others, the 
former becoming completely eaten in midsummer, the latter not until 
toward the close of the season, or remaining only slightly damaged 
until then. In 1882 the leaves were eaten faster than they could be de- 
veloped, and the insect continued abundantenough to prevent a second 
crop of foliage until in November, when it became too cold for the 
leaves and active insects to exist. 
On these grounds the southeast half of each tree has suffered more 
than the northwest half. This peculiarity has been very strongly pro- 
nounced this year, 1883, on all the trees affected, and upon some exam- 
