To determine physical conditions suitable for the culture of Pseudaphycus malinus Gahan, the author dealt with mainly the effect of temperature, humidity and light. Most of the experiments were made at the temperature of 25℃. When the parasites were reared at such three different temperatures as 20°, 25° and 30℃, the number of progeny produced by a single female parasite was the least at 30℃. There was no difference in number between the progeny produced at 20℃ and that produced at 25℃. It is impractical to rear the parasite at 20℃ because the period to complete one life cycle at 20℃ is far longer than that at 25℃. The longevity of the adult has a close connection with the relative humidity which is an important physical factor governing the oviposition of this parasite. According to the present study this parasite was severely affected by the low humidity. The number of progeny produced by a single parasite was the highest at 74% R. H., whereas there was no difference in the number of progeny between the groups reared at 64% R. H. and that at 90% R. H. So far as the author's experiments are concerned, it is too early to derive a result on the difference between the progeny reared under the conditions of periodic illumination and constant darkness, if any. In four cases among nine experiments on the production of mummies by a single parasite, the parasites produced more mummies under the condition of constant darkness than under that of periodic illumination. And among the other four cases no difference could be found between the results obtained from the two different light conditions. There was one case that the number of mummies produced under the condition of periodic illumination was larger than that produced under constant darkness. From these data the author came to the conclusion that a combination of 25℃, 70-80% R. H. and constant darkness is the best condition for the breeding of the parasite. As the surface of the mummy is covered with the white cottony excreta, the mummies were apt to become a mass. This makes it difficult for the parasite to emerge from the mummy. To separate each mummy some masses were put into a glass cylinder containing several sheets of paper with the rough surface and shaked. When the mummies were shaked rudely, percentage emergence of the parasite was checked by wound of the mummy.