Insects of Shade Trees and Their Control. i 
The work of these beneficial insects brings it about that no native 
insect is ever present in destructive numbers for longer than a year or 
two, being by the end of that period greatly outnumbered by its ene- 
mies and rendered practically harmless. This is particularly notice- 
able in insects feeding on leaves and on the outside of the plant gen- 
erally. This is true of all native insects; but not of those that have 
reached our shores from abroad. In the great majority of cases 
these were not accompanied by their home enemies, and this accounts 
for their uninterrupted destructiveness during long periods of time, 
generally until our native insect parasites and predators develop a 
taste for them, or until their more effective home enemies have been 
discovered, imported, and established in their new home, or until 
these have reached us as accidentally as 
did their hosts. 
PREVENTION OF INFESTATION. 
Many shade-tree pests are likely to 
reach the community by way of the 
nursery stock. It is imperative, there- 
fore, to insist that young trees be 
thoroughly cleansed before they are 
_taken from the nursery and certainly 
before they are planted. Inspection 
alone, however, can not always be de-~ 
pended upon, for some insect pests are 
very minute and are apt to hide be- 
yond reach of eye or lens. Fumigation "* ee amaee oe a Hn 
with hydrocyanic-acid gas is at present of apple-tree tent caterpillar. 
in general practice in nurseries and is = P™/8"8et_ (Biske.) 
the most reliable means of freeing stock from infestation. If a tree 
is clean and uninfested at the start, it has stored up vitality which 
will enable it more successfully to resist subsequent attacks. 
CONTROL, PART OF ROUTINE. 
Just as the potato grower in sections of the country invaded by the 
Colorado potato beetle considers spraying a regular, essential part of 
successful potato culture, so the municipality must learn to regard 
regular, periodic inspection of trees for evidence of insect injury, and 
treatment for it, as necessary to the proper care of its shade trees. 
The enlightened, efficient tree warden, after a little experience, sys- 
tematizes this work and dovetails it in with his other duties in such 
a way as to utilize the labor at his command to best advantage with- 
out neglecting other important work. Thus, careful examination 
