Close-range sexual communication of the egg parasitoid wasp Ooencyrtus kuvanae (Hymenoptera: Encyrtidae) takes place on host gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae), egg masses. We tested the hypothesis that mate recognition in O. kuvanae is mediated, in part, by low-volatility cuticular hydrocarbon (CHC) pheromone components. Gas chromatographic and GC-mass spectrometric analyses of body surface extracts of male and female wasps revealed no sex-specific components, but 5-methylheptacosane (5-me-27Hy) and 5,17-dimethylheptacosane (5,17-dime-27Hy) were consistently more abundant in extracts of males. The ratio of 5-me-27Hy and 5,17-dime-27Hy was similar in extracts of males and females, and quantitative differences alone seemed insufficient to impart sex-specific CHC profiles. Therefore, we further hypothesized that the absolute configuration of 5-me-27Hy and 5,17-dime-27Hy contributes to mate recognition or attraction. As the stereoisomers of 5-me-27Hy and 5,17-dime-27Hy cannot currently be separated chromatographically, we could not determine the stereochemistry of the insect-produced components. Instead, we synthesized all stereoisomers and bioassayed synthetic blends in laboratory experiments. Of eight 2-component blends, each blend containing one of the two enantiomers of 5-me-27Hy and one of the four stereoisomers of 5,17-dime-27Hy, the blend of (5S)-methylheptacosane and (5R,17S)-dimethylheptacosane attracted males, whereas the blend of (5R)-methylheptacosane and (5R,17R)-dimethylheptacosane repelled males. Apparent recognition of both pheromone components and pheromone antagonists by males supports the hypothesis that the stereochemistry of 5-me-27Hy and 5,17-dime-27Hy, and possibly other methylated CHCs, may differ between male and female O. kuvanae, and that these differences may serve in mate attraction and recognition.

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Males and females of the parasitoid wasp Ooencyrtus kuvanae (Howard) (Hymenoptera: Encyrtidae) emerge en masse from gypsy moth, Lymantria dispar dispar (L.) (Lepidoptera: Noctuidae: Lymantriinae), host egg masses. Males engage females in a brief pre‐copulatory ritual, mate, and then execute a post‐copulatory ritual. We investigated mechanisms, functions, and fitness consequences of the pre‐ and post‐copulatory ritual by high‐speed cinematography, gas chromatographic‐mass spectrometric analyses of volatile constituents on the insects’ integument, and behavioral assays. Our data indicate that the mechanisms of the pre‐ and post‐copulatory ritual are physical interactions rather than pheromone transfer. During the pre‐copulatory ritual, the males put females into a trance‐like state that persists for some time after copulation. Males attained a mating with in‐trance females 9.5 times faster than with females that had come out of trance. Mated females with post‐copulatory ritual experience did not remate, whereas females lacking that experience did. The total number of offspring and daughters did not differ between females with or without post‐copulatory ritual experience or in relation to the duration of that ritual. The post‐copulatory ritual functions as a form of mate guarding in that the male accelerates awakening of the in‐trance female, which then rejects mating attempts by other males, ensuring his paternity.

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Sperm competition generates selection for male traits to prevent it. These traits remain unclear in species where males compete for a virgin who is briefly receptive. Males of the parasitoid wasp Ooencyrtus kuvanae Howard (Hymenoptera: Encyrtidae) compete over females following emergence from host egg masses. Males engage virgins in a precopulatory ritual, mate, and then immediately perform a postcopulatory ritual after which the female becomes unreceptive. Often, sneaker (M 2 ) males copulate with a female while she is engaged in the postcopulatory ritual, and they also perform the postcopulatory ritual. We investigated (i) paternity of M 1 and M 2 males using DNA microsatellite analysis, (ii) copulation and postcopulatory behaviour of both males, and (iii) morphological adaptations of the aedeagus for sperm removal. Eighty-eight percent of M 1 males sired all daughters when they were first to perform the precopulatory and postcopulatory ritual, suggesting a linked effect of both rituals on paternity. The number and length of copulations by both males did not affect paternity, and the shape of the aedeagus does not seem to facilitate sperm removal. Our results are consistent with the hypothesis that postcopulatory rituals represent forms of mate guarding that function to increase paternity in the context of sperm competition.Résumé-La compétition spermatique entraîne une sélection des traits mâles qui permettent de l'éviter. Ces traits restent obscurs chez les mâles qui font compétition pour une femelle vierge qui n'est réceptive que sur une courte période. Les mâles de la guêpe parasitoïde Ooencyrtus kuvanae Howard (Hymenoptera: Encyrtidae) se font compétition pour les femelles lors de leur émergence des masses d'oeufs de l'hôte. Les mâles entreprennent un rituel précopulatoire avec les femelles, s'accouplent et complètent immédiatement un rituel post-copulatoire à la suite duquel les femelles ne sont plus réceptives. Souvent, des mâles intrus (M 2 ) s'accouplent avec la femelle durant son rituel post-copulatoire et pratiquent aussi eux-mêmes le rituel postcopulatoire. Nous avons étudié i) la paternité chez les mâles M 1 et M 2 par analyse des microsatellites d'ADN, ii) la copulation et le comportement postcopulatoire chez les deux types de mâles et iii) les adaptations morphologiques de l'édéage pour le retrait du sperme. Quatre-vingt-huit pour cent des mâles M 1 engendrent toutes les guêpes filles lorsqu'ils sont les premiers à compléter les rituels copulatoire et postcopulatoire, ce qui laisse croire à un lien effectif entre ces deux rituels et la paternité. Le nombre et la durée des accouplements chez les deux types de mâles n'affectent pas la paternité et la forme de l'édéage ne semble pas faciliter le retrait du sperme. Nos résultats s'accordent avec l'hypothèse selon laquelle les rituels postcopulatoires représentent une forme de surveillance du partenaire dont la fonction est d'augmenter la paternité dans une situation de compétition spermatique.