Asymmetric contests among sawyer beetles (Cerambycidae: Monochamus notatus and Monochamus scutellatus)

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Abstract
Females of both Monochamus scutellatus (Say) and Monochamus notatus Drury (Coleoptera: Cerambycidae) preferred to oviposit in large diameter pine logs. When females of both species were present, oviposition on the largest diameter log by M. scutellatus was much reduced. There were both inter- and intra-specific contests among females, usually over oviposition holes cut by females in the bark. Contests among females occurred disproportionately on the largest logs. Previously inseminated females paired with radiation-sterilized males laid no fertile eggs, supporting the hypothesis that a male is highly likely to fertilize eggs laid by a female with which he is paired. In intraspecific contests among females over oviposition holes and among males over females, a challenger could supplant a resource holder only in an escalated contest. However, in interspecific contests, M. notatus challengers were able to supplant M. scutellatus resource holders without escalation. In both sexes, a contest was more likely to be nonescalated when the resource holder was larger than the challenger. Among males, a larger resource holder was significantly more likely to repel a smaller challenger than was a larger challenger to replace a smaller resource holder.