Before you commit to the need for fumigation, you may want to search for the most reputable exterminators in your area. I recently spoke with six different firms, and find that the answers
they give are very dependent on whether they are highly professional, or simply motivated to
ink a sale.
Unless you ID's the termites or other wood destroying pests as not being subterranean, it's
common for ants to follow and feed on termites. Get rid of the termites, and the ants will leave.
Rather than posioning your whole house, and exposing it to potential explosion, maybe you
get lucky and find out all you need to do is have a pro treat the soil and foundation.
Nothing beats doing your homework before you pay for expensive repairs.