Prolonged Precopulatory Mounting Increases the Length of Copulation and Sperm Precedence in Locusta migratoria (Orthoptera: Acrididae)

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Abstract
The migratory locust, Locusta migratoria Linné, shows not only prolonged copulation but also prolonged precopulatory associations between males and females. To understand the evolutionary significance of these behaviors, sperm competition success, measured by the P2, (i.e., the proportion of offspring sired by the second male to mate), was analyzed using the genetic marker albino. The precopulatory behavior has been proposed to guard a female or ensure timely mating. We report here that precopulatory mounting has a function other than guarding or just waiting in this locust: prolonged precopulatory mounting increases the length of copulation, which in turn increases the P2. Lengths of precopulatory mounting and copulation, as well as nearly absent postcopulatory mounting, were little influenced by the presence of a rival male. The observed large variation in P2 indicates that previously proposed mechanisms for sperm competition are not mutually exclusive, but all could occur in this species.