A trapping method for collecting quantitative samples of insects, especially beetles (Coleoptera) associated with decaying wood or wood fungi, is described. The trap is a modification of the window flight trap, attached to dead tree trunks, preferably close to the basidiocarps of polypores. Sampling during the summer of 1990 in southern Finland showed that large numbers of insects living in decaying wood or polypores can be caught with this method without destroying the habitat. Several threatened species were found during this sampling.