Monsters creating the dungeon as they live, is my passion.
Here is a crapply programmed test I have of various interactions between monsters.
It runs using curses in the terminal.
Right now it randomly introduces creatures but I'm particularly proud of how different subsets lead to distinct dungeon architectures.
To answer your question, dwarf1s tunnel in straight lines until they dig out some gold, then they turn left or right, pick up the gold and spawn a dwaf2. Dwarf2s excavate exposed corners that are not next to doors and build doors at the entrances to open spaces.
This leads to a room and corridor dungeon.
Larva move in an orthogonal random walk, only excavating walls that do not change the connectivity of the dungeon (they can figure this out from local knowledge).
They lead to a maze shaped dungeon.
Ants move in a all-direction random walk, avoid digging walls too thin and dig out larger chambers when next to another ant. this leads to a really cool tunnel effect.
there are many other things that I think are cool that would take awhile to explain.