What does it mean that target species don't get wiped out

[Michael Gochfeld]

I don't agree with the example that since target species don't get wiped 
out by Bt we don't have to worry about non-targets. The target species 
are targets for a very good reason, intrinsic to their population 
biology and their potential for explosive population increase.  Most 
non-target species lack this potential at most times and in most places. 
Thus Gypsy Moths thrive in forests where certain species of butterflies 
might succumb.  This argument applies to any insecticide, not just Bt. 

M. Gochfeld