The results of experiments are presented which suggest that males can discriminate between mates and non-mates. In trials with tethered females, males experienced an approximately 15 min ‘refractory period’ between mating once and remating. When given a choice between a recent mate, and a (recently mated) non-mate ovipositing on their territories, males were significantly more likely to mate a non-mate than a previous mate. The possible mechanisms for discrimination are considered.