I don't think carpenter ants come in for the litter, though perhaps they
are interested in it when they find it.  We just had our house treated for
the ants and were told that they come in through damp wood in the house,
like places around windows and doors that haven't been caulked recently and
are letting in moisture.  If you see several at one time in the same room,
you have a nest in your house somewhere.  The individual ants are just
wandering in from outside.
 
Blessings
Judith
[Posted in FML issue 3126]