For the first time, the biotopic associations of xylophilic druid fly larvae (Diptera: Clusiidae) with decaying wood, habitat conditions in wood, and trophic associations have been described. The features of the formation of the clusiid community and its composition are considered. For the first time, detailed information is provided about the species of insects (Coleoptera, Diptera) co-occurring with the clusiids in rotten wood.