This is pretty cool:

Tiny robots programmed to act like roaches were able to blend into cockroach society, according to researchers studying the collective behavior of insects. Cockroaches tend to self-organize into leaderless groups, seeming to reach consensus on where to rest together.
For example, when provided two similar shelters, most of the group tended to gather under the same one.
Hoping to learn more about this behavior, researchers led by Jose Halloy at the Free University of Brussels, Belgium, designed small robots programmed to act like a cockroach.
The robots didn’t look like the insects and at first the roaches fled from them, but after the scientists coated the robots with pheromones that made them smell like roaches the machines were accepted into the group, nesting together with the insects.