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first done in this department, when 12 men were employed to clean the 
trees, benches, walls, and stonework in the parks. The first autumn of 
our work we collected 13 bushels of these cocoons and egg masses, leav- 
ing those cocoons that were apparently parasitized until the final clean- 
ing. The large elms on the Mall were thoroughly cleaned with steel 
brushes made for the work, and each tree received a wash to destroy 
any insects that might be in the crevices of the bark. This work of 
collecting (and burning in the furnace) has been carried on each year as 
the force would allow, in this way keeping them in subjection. We 
now treat them in four different ways: 
(Ist) By hand-picking, of which bushels are each year taken from the 
trees with tools especially adapted for this work. 
(2d) By jarring the larve down with a pole, so arranged that a 
blow from a mallet on a projection placed at the large end of the pole 
will jar any down that may be on the branches. With a sudden blow 
‘most of them will fall to the ground, when they can be crushed. 
(3d) By poisoning the foliage with London purple, which is quite 
effective and used especially on very large trees that can not be treated 
otherwise. 
(ith) By poisoning or spraying the trunks of large trees with an 
emulsion of petroleum and ecarbolic acid. This penetrates most of the 
cocoons sufficiently to kill the inmates, the disadvantage being that 
it kills the parasites too. This method is only resorted to when the 
egg masses are very numerous and we are short of help, and as a means 
of reducing the next brood. Large numbers of trees were so treated 
this season to arrest the late summer hatchings. 
The next insect in abundance and destructive working was the Bag 
Worm, Thyridopteryx ephemereformis. Whole portions of the parks 
were literally stripped of their foliage; many of the trees on the drives 
were nearly as bare as in winter. So abundant were they that the 
branches were strung with their cases, and with one push ofthe instru- 
ment prepared for collecting them, a handful of these cases would be 
taken. Four kinds of tools were made for this work, and the cases were 
collected and destroyed. In this way nearly 22 bushels have been col- 
lected and destroyed. 
The Datanas have always been abundant in the parks, and as many 
as 15 pounds of caterpillers have been taken from a single tree. These 
are collected while massed, as is their habit, and then destroyed. 
Hyphantria cunea is very abundant in our parks ard has been de- 
stroyed by cutting down the webs as far as was possible. if the tree 
was too valuable, they have been twisted out with poles made especially 
forthis work. In some cases spraying has been resorted to, but as this 
does not remove the unsightly web, the most practical thing to do is to 
remove the whole colony. 
Clisiocampa americana has this year appeared in our parks for the 
first time, and in great abundance. The webs that appear on the trees 
