Homeowners in Vancouver are fighting a growing infestation of pesky carpenter ants.

A combination of unusually mild weather and the recent heat spell allowed the insects to flourish in British Columbia's Lower Mainland. Left unchecked, the ants can tunnel through wood, which they use for nesting sites. Sawdust may be all that is left.

"We've had to call structural engineers," said exterminator Jason Page of Canadian Pest Control. He said the ants weakened one house to the point where it leaned too far to one side and was beyond treatment.

Carpenter antCourtesy: Clemson University/USDA

Homeowner Carole Smallwood said she's never seen so many ants swarming along the side of her house. Exterminators say their business has doubled in the past year.

Pest controllers say carpenter ants can enter on firewood, through cracks and on tree limbs or wires that touch the house. The pests are attracted to wood that has been exposed to moisture.

To prevent an infestation, experts suggest:

• Keep trees and shrubs back from touching the house
• Remove old firewood
• Remove possible food sources such as meat products, grains and sweets

A full treatment for carpenter ants can cost several hundred dollars.