32 THE BOX-ELDER LEAF-ROLLER IN 1896. 
As the worms travel about considerably it was thought 
that raupenleim, which is a thick, viscid, tarry substance 
made during the process of refining petroleum, would pre- 
vent the ascent of the young caterpillars from the egg-mass- 
es, which are laid on the rough bark, to the smaller branches. 
Rings of raupenleim were accordingly spread around all the 
larger limbs and upon as many of the smaller ones as possi- 
ble; this was done before the eggshatched. Foursmalltrees, 
about fourteen feet high, and two very large trees, were thus 
treated on April 26th. On May 13th, no effect of this ap- 
plication could be detected. The failure of the raupenleim to 
catch the insects was largely due to the dusty condition of 
the streets at that time, as the dust, blown about by the 
winds, was caught by the sticky material and soon changed 
its surface into a crust over which the insects passed in safety. 
On May 1st the eggs began to hatch and on May 7th 
the young caterpillars had commenced to curl the leaves and 
to eat them. On May 13th four small trees on St. Alban’s 
street in St. Paul were sprayed with Paris green and water, 
using a level teaspoonful of Paris green to a pailful of water. 
A quantity of milk of lime was added, using about twice 
as much lime by weight as Paris green. Six hours after 
spraying rain fell and continued to do so for several days, 
so that the Paris green was almost completely washed off, 
but the interval between spraying and the rain was sufficient 
to poison and destroy nearly allcaterpillars. Afewremained, 
however, and on May 25th the spraying was repeated. This 
time the Paris green remained on the foliage longer and only 
a very few caterpillars escaped death by poisoning, and 
these were killed later by a third spraying. 
On June 6th two large trees on University avenue were 
sprayed with Paris green of the same strength; unfortunate- 
ly a very heavy rain fell within two hours after the spray- 
ing and it was feared that the work had been done in vain, 
but as an inspection showed later, the time had been sufficient 
to kill the great majority of caterpillars, and in a few weeks 
afterward the trees showed a marked superiority over those 
not sprayed. 
The above experiments demonstrate that this destruc- 
