A carnivorous plant must attract, kill and digest prey. It must then also benefit from digesting the prey. In most cases, this will yield amino acids and ammonium ions. There are some cases, where plants catch the prey, but they do not digest it. Rather, they have a symbiosis with another organism, which feeds on the prey. One such case is the species of the sundew "Roridula", which forms a symbiosis with the assassin bug. The bugs eat the trapped insects. The plant benefits from the nutrients in the bugs' faeces.