By nature of their conspicuousness, sexual signals can cause a conflict between natural and sexual selection, with natural selection favoring a decrease in exaggeration of an ornament and sexual selection favoring an increase. The Pacific field cricket, Teleogryllus oceanicus, is subject to an acoustically-orienting parasitoid fly where it has been introduced in Hawaii, making calling particularly risky. A novel obligately silent male morph, controlled by a single sex-linked gene, evolved within just 20 generations in some populations in Hawaii. These flatwings are protected from parasitism, but face difficulties in mate attraction and courtship. Such problems may have been overcome, and the rapid evolution of a sexual signal facilitated, by pre-existing behavioral plasticity, with individuals responding to silent environments, like those with the flatwings, by altering their response to conspecifics. Variation in this plasticity could explain the paucity of examples of rapidly-evolving secondary sexual characteristics.