The hindgut of the diplopod Pachyiulus flavipes is inhabited by specific yeast populations. The yeast communities consist almost exclusively of ascomycetes, viz., Debaryomyces hansenii, Torulaspora delbrueckii, and Zygowilliopsis californica. Evidence is provided that the yeasts isolated from the gut can be considered symbionts that remain in a steady state under different feeding and rearing conditions.