Lost - spider bite couple?

does anyone remember that one episode where it was dedicated to this couple, i think they had some diamonds, but in the end they got buried alive because the others thought they were dead because of these spider bites. what on earth happened to them? because they surely cant have wasted a whole epsiode on a threadless pointless story line? and since no one actually seems to proepr die on this island, im sur ethere must be more to it??