First record of predation by <i>Anoplotrupes stercorosus</i> (Coleoptera, Geotrupidae) on a slug species of the genus <i>Arion</i> (Stylommatophora, Arionidae)

The beetle Anoplotrupes stercorosus inhabits European forests, preferably in cool hardwood and mixed environments. Larvae are strictly coprophagous while adults exhibit a varied diet that includes dung, decaying organic matter, and fungi. In mountainous areas, they are present in advanced stages of carcass decomposition, highlighting their ecological relevance as a decomposer. In Navarra (Spain), a unique behavior is reported. It has been observed that A. stercorosus attacked slugs of the genus Arion, which are larger than the beetles, and subsequently nested beneath them. This finding provides new insight into the ecological role of A. stercorosus and expands knowledge about its diet and trophic plasticity. Key words: Dung beetle, Diet, Ecological plasticity, Palearctic, Iberian Peninsula