The effect of mold, microbial pesticide Verticillium lecanii F126-12-3M on the egg-production of rotifera Philodina erythrophthalma, contributing to purification of wastewater was examined in batch culture experiment. The result indicated that the number of eggs was several times higher in the cultures with supernatant of mold than those of the control. It was found that there was a substance stimulating the production of eggs in the supernatant of mold culture. The supernatant of mold culture was found to be of importance for egg production. The egg of P. erythrophthalma, the reproduction of which was promoted by addition of mold culture, could survive under desiccation for five days. It was suggested that mass cultivation of P. erythrophthalma could be accomplished using this method.