The effect of female mating history on sperm precedence in the two-spot ladybird, Adalia bipunctata (Coleoptera, Coccinellidae)

Effects of two different mating regimes on sperm precedence in the two-spot ladybird, Adalia bipunctata, were studied using the polymorphic gene for melanism as a marker for paternity. Virgin nonmelanic females (homozygous recessive) were mated to nonmelanic male(s) and then, after laying fertilized eggs, were mated to a melanic male of known genotype. The results after the two successive single matings showed a highly variable degree of paternity of the second male. Initial multiple mating with nonmelanic males did not alter the pattern of paternity after the subsequent single mating with a melanic male, but it had two other effects: (1) the female showed an increase in rejection behavior, and (2) a longer copulation was required for high success of the melanic male. Additional observations in which families were reared from beetles collected in copula in the field demonstrated that sperm competition also occurs under natural conditions. The outcome of the competition was variable with frequent sperm mixing.