FEMALE PREFERENCE FOR THE PHEROMONE OF MALES WITH LOW FLUCTUATING ASYMMETRY IN THE JAPANESE SCORPIONFLY (PANORPA-JAPONICA, MECOPTERA)

Fluctuating asymmetry (FA) is defined as small, random deviations from perfect bilateral symmetry in a bilaterally symmetrical morphological trait. The relationship between FA in forewing length of males and the relative sexual attractiveness of their pair-formation pheromones was studied experimentally in the Japanese scorpionfly, Panorpa japonica. This is the first study of the role of FA in pheromonal communication systems, and one of only a few studies on the relationship between FA and sexual selection. Collectively, the results of four interrelated experiments reveal that females prefer the pheromone of males of relatively low FA in forewing length. The experimental manipulation of forewing FA of males by cutting wing lengths did not influence their olfactory attractiveness to females. In this case, females chose the male with the lowest premanipulation FA. Thus, natural wing length FA apparently is correlated with inherent differences between males that influence the properties of sex attractant males produce. Female preference for low-FA males may be adaptive as a result of material and/or genetic benefits received by females.