Males of the bushcricket, Requena verticalis, contribute parental investment at mating via a nutrient-rich spermatophore. Because the first male to mate has a high confidence of paternity, subsequent males have their investment cuckolded. The effects of first male sperm precedence on male mate choice and protandry were investigated. Males were equally likely to mate with virgin and non-virgin females during mating trials. However, they could discriminate on the basis of female age and mated preferentially with young females in laboratory trials and in the field. By using age as a cue, males increase the probability of rejecting non-virgin females, thereby reducing the risks of cuckoldry. It is argued that failure to recognize non-virgins per se may have arisen by sexual conflict over mating, and that the high degree of protandry is an adaptive strategy by males to mate with their preferred young females and enhance their confidence of paternity.