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 accordingh^ spread around all the 

 larger limbs and upon as many of the smaller ones as possi- 

 ble; this was done before the eggs hatched. Four small trees, 

 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, 

 bvit the interval between spraying and the rainw^assuihcient 

 to poison and destroy nearly all caterpillars. 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 hj poisoning, and 

 these were killed later by a third spraying. 



On June 6th two large trees on University avenue ^vere 

 sprayed with Paris green of the same strength; unfortunate- 

 ly a very heav3^ rain fell within t\vo hours after the spray- 

 ing and it v/as 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 fe-w weeks 

 afterward the trees showed a marked superiority over those 

 not sprayed. 



The above experiments demonstrate that this destruc- 



