adam the problem with most pest control agents is that it gets into the soil and when the insects borrow or play in the soil trace elements of the chemicals are attached to them, in most instances they stick to their bodies and never enetr their respiratory systems..
What this means is that they will have the chemicals on them but will not die, when you feed them to your reps the chemical is passed on..
That is why six months is a minimum period to wait (and i stress minimum) because by then the pestacides are broken down by the elements.... (personally i would wait 12 months, but hey thats just me)