Females prefer large and symmetrical ornaments. Thornhill, R. 1992. Fluctuating asymmetry and the mating system of the Japanese scorpionfly, Panorpa japonica . Watson, P. J. and R. Thornhill. Fluctuating asymmetry and sexual selection.
Female preference predates the evolution of the sword in swordtail fish.
Marler, C. A., and M. J. Ryan. 1997. Origin and maintenance of a female mating preference. Sexual selection, receiver biases, and the evolution of sex differences. Pitnick, S. and W. D. Brown.