FEMALE CHOICE FOR AN INDICATOR OF MALE SIZE IN THE SONG OF THE BLACK-HORNED TREE CRICKET OECANTHUS-NIGRICORNIS (ORTHOPTERA, GRYLLIDAE, OECANTHINAE)

The calling song of male crickets, including Oecanthus nigricornis (Wa lker), attracts females for mating and provides a model system of sexu al communication. We give the first conclusive identification of a fea ture of cricket song that is both attractive to females and indicates a phenotypic feature (body size) that determines male mating success a nd female reproductive benefits. We do this by first testing for corre lations between song characteristics and aspects of male phenotype tha t are hypothesized to indicate male quality. We show that song is a re liable indicator of male size and male age, and that large male size i s associated with increased female fecundity. We then use playbacks of synthetic songs that mimic natural Variation in song parameters to st udy song preferences and we compare preferences under different presen tation regimes to determine whether choices are based on relative song quality or some fixed criterion. Females show a preference for the lo wer frequency songs produced by large males, but only during simultane ous playbacks. Thus female choice is based on the relative quality of calls that can be sampled simultaneously. These results provide strong support for the hypothesis that females use variation in calling song to assess male mate quality.