Sexual selection in Cnephasia jactatana (Lepidoptera: Tortricidae) in relation to age, virginity, and body size

Darwin suggested that females should be more selective than males when choosing mates because eggs cost more than sperm, females mate fewer times, and females undergo most of the parental care. We studied sexual selection in a New Zealand leafroller, Cnephasia jactatana Walker, in relation to age, virginity, and body size in the laboratory. Results show that males significantly preferred young and virgin to old and mated females for mating, suggesting that the reproductive fitness of females depends strongly on their age and virginity. Female significant preference for virgin males regardless of male age indicates that male virginity and age have asymmetric effects on male reproductive fitness. Higher mating success in males with longer antennae, regardless of male body weight, suggests that male antennal length rather than body weight plays an important role in sexual selection. The similar antennal-wing length relationships between selected and nonselected males suggest that the absolute length of both antennae and wings are selected characters in male mating success. Males selected mates according to their own and their partners' body weight but did not have significant preference for females' antennal length and antennal/body length relationships, suggesting that body weight, rather than morphological features, plays a major role in female mating success. In the sexual selection of C. jactatana, males seem to be the choosier sex as a result of (1) females varying more in quality than males and (2) fertile spermatogenesis occurring exclusively during the pupal stage, potentially leading to sperm limitation.