EFFECTS OF YEAST ON THE GROWTH AND REPRODUCTION OF THE SAPROPHAGOUS MILLIPEDE POLYDESMUS-ANGUSTUS (DIPLOPODA, POLYDESMIDAE)

The millipede Polydesmus angustus was reared in the laboratory from ha tching to maturity, reproduction and death. Two food types were used: dead leaves alone or dead leaves supplemented monthly with dry food ye ast (Saccharomyces cerevisiae) at a rate not exceeding 5% of leaf dry weight. Growth, survival, adult live weight and fertility were compare d between females reared on the two diets. Although the species was ab le to complete its life cycle on dead leaves alone, several parameters were strongly affected by the addition of yeast: growth was significa ntly faster, adult females became significantly larger and there was a 4.3-fold increase in fertility. Only survival was unaltered by the ad dition of yeast. The comparison between these laboratory results and f ield data on female fertility and live weight suggests that the natura l diet of millipedes includes foods of higher quality than dead leaves . Possible sources of high-quality food in natural conditions are disc ussed.