Intraspecific competition and possible cannibalism in the six-spotted spider mite Eotetranychus sexmaculatus (Acari: Tetranychidae).

Intraspecific interactions in spider mites (Acari: Tetranychidae) often involve competition, particularly among males during mating, although cooperative behaviors such as webbing for defense have also been reported. When studying the six-spotted spider mite, Eotetranychus sexmaculatus (Riley), we observed an unexpected case of conspecific egg cannibalism by an adult female, a behavior rarely documented in spider mite species. To investigate the ecological mechanism of this phenomenon we conducted two oviposition experiments under controlled conditions. The 'single-female oviposition test' revealed that unfertilized females laid significantly fewer eggs than fertilized ones, and that male presence did not affect offspring survival or sex ratio. The 'multiple-female oviposition test' demonstrated that increased female density negatively affected oviposition rate and survival, particularly after 3 days. Although egg cannibalism was infrequent, it was more pronounced under higher competition levels. We also recorded lethal male-male combat, a previously unreported behavior in E. sexmaculatus. Our findings suggest that intraspecific interactions in E. sexmaculatus, including cannibalism, may be linked to competition for space and resources. Future studies should explore the adaptive significance of these behaviors and their potential role in population dynamics. [ABSTRACT FROM AUTHOR]