Host tree preferences of hermit beetles (Osmoderma eremita Scop., Coleoptera: Scarabaeidae) in a network of rural avenues in Poland

The occurrence of Osmoderma eremita (Scopoli, 1763), an endangered species restricted to hollow trees, was studied in a network of rural avenues in northern Poland. We detected 1002 trees with hollows suitable for hermit beetle development (25% of all trees). Among them, 114 (11%) were occupied by O. eremita. The distribution of O. eremita was not random with respect to tree species identity. Tilia cordata and Alnus glutinosa were preferred while Acer platanoides and Carpinus betulus were avoided. The beetle preferred trees about 450 cm in circumference at 1.3 m height with a tendency towards lower occupancies of the biggest trees having circumferences above 500 cm. O. eremita did not show any significant preferences according to hollow entrance area, exposition and road surface type. Contrary to common belief O. eremita did not prefer oaks. Our results show that preservation schemes and choices of prime areas for conservation for hermit beetles have to include stands of trees other than oak.