Male bushcrickets, Requena verticalis, provide their:mates with a proteinaceous nuptial gift, which functions both as paternal investment in offspring and to ensure sperm transfer. When nutrients are limited, males have a lower potential reproductive rate than females, so the operational sex ratio becomes female biased. Males are then expected to discriminate more in their choice of mate for two reasons: (1) the relatively higher female potential reproductive rate should reduce the costs of rejecting a female; (2) multiple mating by females should increase variance in female mate quality, because of first male sperm precedence. Males are known to discriminate against old females, which are more likely to have mated previously. Our objective in this study was to partition experimentally the influences of male potential reproductive rate (manipulated by diet) and variance in female quality (estimated by age) and to assess their relative influence on the level of mate choice of male bushcrickets. The potential reproductive rate of males had a great impact on their choosiness, whereas variance in female age had no effect. These results support recent theoretical models that predict costs, rather than benefits, will primarily influence the level of mate choice; (C) 1998 The Association for the Study of Animal Behaviour.