"Walter R." wrote in message
...
That's a good question. The answer is simple: You don't know where their
nests under the house are. They dig tunnels through the soil under the
house and when they emerge somewhere, they build their own tunnels of
muddy earth. During their mating season, March/April, they swarm and build
more tunnels, using the debris of the stuff they tunnel through, like wood
or wallboard. Nasty critters, causing more damage than all the hurricanes
and tornadoes together. Therefore you have to poison a fairly large swath,
or all of the soil, under/around the house

Not so much all the ground under if you do the perimeter. You have to go
down a couple of feet though, for best protection. I did my last house
when Chlorodane was still available and never had a crawling bug of any sort
after that.