What are these robots and what do they do?
They are in the scene where the human babies are grown by the robots. They don't look mechanical,but I am guessing that they are part of the process for making humans, maybe cleaning robots.
There's actually a bit of backstory to these little critters that didn't make it into the film. In short, they're robotic parasites.
Barrow: Larry and Andy [Wachowski] talked about how the creatures were constantly changing and shimmering as in this drawing, where there's a lot of little robots crawling all over the Fetus Stalk, like arachnids
Amongst these robots, there's a sort of pecking order. This doesn't fully come across in the movie, but it's part of the backstory Larry and Andy have come up with. Some of the robots are bad and are actually siphoning off energy, so other robots come along and pick them off.
They also talked a lot about there being a bit of prejudice amongst the robots, those that have developed less than humanistic forms look down on the ones with a vestigial human appearance
Images from 'The Art of the Matrix'