What’s in a Carpenter Ant “Dump Pile?” 

By Chris Williams on October 8, 2014.
carpenter ant frass or boring damage

Boring damage from carpenter ants

Sometimes the first indication that carpenter ants are nesting in a home is the sudden appearance of piles of sawdust on the floor. You don’t pay much attention at first. Not until you realize that you have swept the same piles up two or three times do you start wondering where they are coming from. A number of wood-boring insects can leave sawdust piles, including carpenter ants.

A carpenter ant colony’s sawdust pile is basically a garbage heap of unwanted debris, called a “dump pile,” that the ants push out of their nest. It typically contains wood parings (looking like coarse sawdust), dead carpenter ants, other dead insects or insect parts, bits of insulation or soil, or whatever else is in their way. The presence of dead insects in the sawdust piles is one clue that it is from an ants’ nest and not from powderpost beetles or from the house “settling.”

Sometimes the carpenter ants’ dumped material is called “frass,” even though the wood particles have not passed through the ants’ digestive system since they do not eat the wood. The wood in a dump pile is literally “sawdust” resulting from the carpenter ants’ excavation efforts to create space for galleries. Carpenter ants like their galleries clean so they get rid of all those gnawed-off wood bits as they remove them.

The “Dump” Can Help Locate the Nest

The carpenter ant nest will be located somewhere directly above the dump pile but it may not be visible. Besides the dump pile below, the only clue might be a slit in the wood (called a “window”) which is the opening that the ants use to eject their garbage. The window is sealed up after use. The wood above the dump pile may have a blistered surface appearance, or it may look perfectly normal…until you break it open. If you pound on the wood, you may hear rustling sounds from the ants inside.

If you find a small pile of wood debris that you think might be from carpenter ants or other insects, you need the help of a professional exterminator to verify the source. A carpenter ant dump pile is a reliably positive indicator of an indoor infestation that needs to be eliminated.

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Photo: Edward H. Holsten, USDA Forest Service,



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