Relative frequency of independent variable classes related to (red bars) biological control agents, (blue bars) biological control targets, (green bars) host plants of targets, and (black bars) management A agent feeding strategy B agent host range C life-stage killed by the agent D parasitoid feeding behaviour E parasitoid brood size F parasitoid attack strategy G target feeding guild H target host range I target voltinism J plant attacked by target K plant parts attacked by target, and L number of introductions within agent-target combinations.