The extent to which a trait deteriorates in response to stress can indicate its fitness importance. Food limitation is a naturally-occurring stress in the katydid Kawanaphilanartee (Orthoptera: Tettigoniidae) and should cue larvae as to the level of sexual competition expected; hunger drives adult females to compete for copulations and thus acquire spermatophore meals. This increases sexual selection on females relative to males for increased body mass. As predicted, under experimental food-stress larval female K. nartee showed little loss of mass whereas male mass decreased. In contrast, the sizes of body parts less critical to mating success showed similar decreases in males and females. For katydids such as Conocephalusnigropleurum, where reversals in mating roles do not occur, larval food stress should result in a greater preservation of male body mass, an important trait in male mating success. This prediction was supported; male mass decreased less than that of females.