sion as rapidly as funds will permit. Unfortunately, a con- 
siderable number of the existing trees are in such bad con- 
dition that they will have to be removed. In the replanting 
of the City, Carolina poplars and silver maples will also 
be removed gradually, to permit the systematic planting of 
better trees. To prevent the further injury of existing 
trees each tree will be provided with a tree guard. While 
the law directs that the cost of tree guards and of planting 
and removing trees is to be charged to the property owners, 
the latter will be given the opportunity, if they so desire, of 
making their own arrangement, subject to the approval 
of the Commission, for this work, otherwise the Commis- 
sion will do it at cost. Emergency work will be done by 
the Commission. 
Injurious Insects. Injurious insects are responsible for 
the poor condition of many of the trees. The tussock moth 
caterpillar, imported originally from Europe, has been for 
a generation a scourge to the trees in Philadelphia. Swarm- 
ing over the foliage in the early summer, they devour the 
leaves with amazing rapidity. While this does not kill the 
trees immediately, it weakens them seriously and in time 
causes their death. As these caterpillars remain over winter 
on the trees in the egg state, they may be readily destroyed 
by gathering the conspicuous masses of white eggs. Many 
may also be killed in the summer by spraying with ar- 
senate of lead. Both methods will be used by the Com- 
mission. In the spring, banding the trunks of the trees 
with ''tanglefoot" is helpful, if the trees have first been 
cleaned of all eggs. The plant lice, which attack the 
plane, Norway maple and other trees, sucking out the 
sap from the leaves or twigs and letting it fall as a sticky 
deposit on the pavement, can best be destroyed by spraying 
with a kerosene emulsion or whale oil soap. Eor the 
various scale insects, which attach themselves to the limbs 
