62 CONTROL BY MECHANICAL MEANS 
such as the shot-hole borer. The limbs or trees removed should be 
converted at once into cordwood and burned. Otherwise, little will 
be gained by their removal. 
Use of Traps 
The kinds of traps are legion, and range all the way from chips or 
stones placed in the garden for squash bugs to hide under to more or 
less ingenious devices for capturing roaches and flies. Many are 
efficient, though it often seems that new individuals make their appear- 
ance about as fast as the others are caught. At best the total numbers 
merely are reduced. 
A variation of trapsisseen in the use of trap crops. By this device 
some kind of plant is introduced that the pest is fond of, and after the 
insects have collected on these plants, they are destroyed by poisoning, 
burning, or by spraying them with some oil or corrosive, such as pure 
kerosene. In other cases the trap precedes the regular crop, and 
thus diverts attack from the more valuable plant. Thus, early kale is 
sown in fields that later are to be set out to cabbages, in order to attract 
the overwintering adults of the harlequin cabbage bug. 
