Ants
A colony is one queen and her daughters, and the tunnelling is most of what you watch. Kept in a formicarium, where the nest is the exhibit as much as the animal.
Overview
An ant colony is one family. The queen is the mother of every ant in it, the workers are all her daughters, and none of it is a pet in the way a hamster is a pet. What you keep is a small society behind glass, and the tunnelling is most of what you watch.
The lifespans are the part that surprises people. Black garden ant queens, Lasius niger, have survived as long as 29 years in laboratory colonies, while workers from the same nest live one or two years under the same conditions. A colony started this spring can still be running when the shelf it sits on gets replaced, as long as the queen keeps laying.
Temperament
Nothing happens for the first few weeks, and that is the colony working correctly. A founding queen shuts herself into a small chamber, lays her first batch of eggs and raises them on her own reserves without going out to feed. There is nothing to see until those first workers walk out.
After that it changes character completely. Workers lay scent trails to whatever you put in the foraging area, carry brood between chambers as the temperature shifts through the day, and swarm anything alive that lands in there. They are not interested in you, and with this animal that is the point rather than a disappointment.
Care and grooming
Two foods, more or less. Something sugary for the workers, which in the wild is mostly honeydew from aphids, and insect protein for the brood, which is what actually grows the colony. Feed protein and you get eggs. Feed only sugar and the colony coasts.
Take uneaten insects out before they mould. A formicarium is a warm damp box, mould spreads in one quickly, and the colony cannot leave. Nothing that cleans a kitchen goes near it either, since the whole nest breathes the same air.
Living and exercise
A formicarium is two connected spaces: a nest where the tunnels and the brood are, and an open foraging area where food and water go. The nest wants to be damp, the foraging area wants to be dry, and the workers sort out the rest themselves.
Escape is the design problem. Ants are small, they climb, and a lid that holds a hamster does not hold these. Most setups use a barrier around the top of the foraging area and a tight seal everywhere else. Keep the whole thing out of direct sun, because a glass nest in a window cooks.
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