If small ants continue to be found in the kitchen even when food is put away and bait is out, should we look for a nest?
You could try, but that’s time-consuming and very difficult. Ants will make nests anywhere—in the walls, in the ceiling, under the floor, or outside the cottage.
If your bait traps aren’t working, you may be using the wrong kind of trap. Different ants have different food preferences. These guests sound like little thief ants (they’re very tiny and yellowish-brown). These ants prefer grease-based food. They could be odorous house ants (darker in colour, and they smell pungent when crushed). The latter like a balanced diet, so put out both protein-based and sugar-based traps to give them more choice. You may have to try a few different kinds of traps.
A microscopic crumb is an ant-sized meal, so keep up your cleaning efforts—otherwise enticing the ants with bait is like offering them broccoli instead of a chocolate fountain.