Originally testing out the idea with simulated crab swarms, the OR gate is the place where one or two crab swarms are merged into a single one, and it worked successfully each time. As for the far more complicated AND gate, it will require the combined swarm heading down one of three paths, and naturally, was not as reliable as the OR gate. When experimenting with swarms of 40 actual crabs which were placed at the entrances of the logic gates, where they were prodded to move along by a looming shadow that resembled a predatory bird overhead, the end results were pretty close to what the simulation came up with.
Seems like crab-powered computers are a very real possibility in the future, although there would be a fishy smell about it.