I recently moved a one hundred year old barn.I have the timbers stacked up and covered with tarps. The rain has got under the tarp and got a few timbers wet. At these wet spots I have found hundreds of little brown ants about 1/4" long and little piles of very very fine saw dust. Can any one tell me what this is? I can't see any other insects. Should I isolate these timbers from the rest? John.