Abstract
The adult Arthropoda occurring in, on, or emerging from 2,660 sporophores of the bracket fungus Polyporus betulinus (Bull.) Fr., growing on dead birch, are listed. Collections were made in New Brunswick, Quebec, Ontario, and Manitoba. Two hundred and fifty-seven species of Arthropoda, mainly insects and mites, were recorded; over 49,000 specimens were examined. Old, twice-wintered sporophores produce more species and more individuals. In general, the fungus is rich in species but rarely produces sizable populations of any one species.