Eur. J. Entomol. 107 (1): 61-64, 2010 | DOI: 10.14411/eje.2010.007

Intrasexual fighting and mounting by females of the horned beetle Trypoxylus dichotomus (Coleoptera: Scarabaeidae)

Yutaka IGUCHI
Laboratory of Biology, Yamashita-cho 1-10-6, Okaya City, Nagano Prefecture, 394-0005, Japan; e-mail: bio-igu@f8.dion.ne.jp

Although females of the horned beetle, Trypoxylus dichotomus septentrionalis, have only small horns they often fight over access to feeding sites by head-butting each other. In addition, they sometimes show intrasexual mounting. In this study 82 females of different sizes were used to determine the relationship between fighting and mounting. Large females more often won fights and so gained access to food than small females. In contrast, small females more often mounted large females and then gained access to food than large females. These results suggest that female mounting may function as a tactic for reducing intrasexual fighting between small and large females.

Keywords: Scarabaeidae, Trypoxylus dichotomus septentrionalis, horned beetle, female intrasexual fighting, female intrasexual mounting, alternative tactic

Received: July 2, 2009; Accepted: November 18, 2009; Published: February 15, 2010

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