Interrupted Matings and the Effectiveness of Second Inseminations in the Twospotted Spider Mite1

Abstract

Competition between males of Tetranychus urticae may lead to disrupted matings in which an intruder replaces the original male and inseminates the female a second time. It is estimated that in crowded populations about 14% of the females are doubly inseminated at emergence. The success of second matings depends upon how soon after the onset of the first copulation the interruption occurs. When progeny of mixed parentage are produced, the relative effectiveness of the first mating is greatest early in oviposition. Apparently, the sperm stores from a complete first mating become depleted in older females, but even so, such females cannot effectively mate again. These findings are interpreted in light of male competition and precopulatory behavior.