Extended Data Fig. 1: Arrangement of installations per site and per treatment.

a, Each site received three installations of three treatments randomly assigned to a 3 × 3 grid. b–d, Treatments included closed cages to exclude insects (b), open cages providing similar microclimatic conditions as closed cages but giving access to insects (c) and uncaged bundles of logs (d). Cages measured 40 cm × 40 cm × 60 cm and were made of white polyester with honeycomb-shaped meshes with a side length of approximately 0.5 mm. Open cages had four rectangular openings measuring 3 cm × 12 cm at both front sides and four rectangular openings measuring 10 cm × 15 cm at the bottom representing in total 6% of the surface area of the cage as well as a total of ten 12-cm slits at the top and long sides. All cages were placed on a stainless-steel mesh (0.5 mm mesh width), which had the same openings as the bottom side of the cages in the open-cage treatment. Photographs show the site in the Bavarian Forest National Park, Germany.