 This discrimination is reminiscent of the Fisherian runaway model, as females may choose for long tails based solely on inherited desirability, and would want to pass on that trait, which would improve the sexual success of their male progeny.This also could be an example of the “good genes” model of sexual selection, as correlations have been found between sperm tail length and the physiological condition of the male.In the case of the Neriid fly, "Telostylinus angusticollis," males have been observed to have coevolved to have a flexible aedeagus.