The presence of the jeweler's loupe here is a hint that this is a very small organism. We generally think of ants as small animals, but this species is the smallest I've ever seen. Each worker is just about 1 mm in length.
Their size and distinctive coloration--dark in the front with light legs and abdomen--identifies them as ghost ants Tapinoma melanocephalum*. Like many inhabitants of the great indoors, their origin is not precisely known. They are from the Old World Tropics for sure, narrowing it down to roughly a third of the surface of the planet.
A colony could form in a pile of dead leaves, or in between a plant pot and it's protective liner. As long as the place is warm and humid, the ghost ants can live happily, feeding on miniscule amounts of sweet things and dead insects. When a colony is successful, some amount of it departs to become a new colony--"budding" instead of the complex new colony creation that some other eusocial insects endure. Besides all the tropics and heated greenhouses in the world, ghost ants live in Florida and Texas, and appear to be spreading.
* Humble and dark-headed