Mud tubes such as these on foundation walls indicate termite activity.
Subterranean termites found in the northeast United States are by far the most damaging of any type of termite. Residential repairs from termite damage are estimated to be in the billions annually.
Subterranean termites are native soil inhabiting insects that feed on wood paper and similar cellulose containing material. Therefore homes that have wood members in close proximity to soil are particularly vulnerable to termite attack. Infestations usually start at the sill plate above the masonry foundation then move to other important load bearing elements.