The adults of Nemophora raddei Rebel appear from the beginning to the middle of April on the campus of Hikosan Biological Laboratory (670 m. in altitude), and visit the pistillate flowers of Salix Sieboldiana Blume in the sunny daytime. The female deposits her eggs in the ovaries of the same plant. Newly hatched larva devours the ovule and the inner wall of the ovary. After the first moult, the larva constructs a small, flat, oval case with the downs of inside or outside of the ovary by spinning its silk and decends to the ground. The larva prefers to feed dead leaves of Castanea crenata Sieb. et Zucc. and Salix Sieboldiana Blume on the ground, and enlarges the case by joining lunate pierces which are cut from the dead leaf. The larva grows to the 6th instar (the last instar) from the beginning of August to September, and the end of the case is fastened to a suitable place by the silk from the beginning to the end of October. The mature larva pupates from the end of October to the beginning of November, and passes over the winter in this state, and the adult makes appearance in the following spring. The egg is shown in Fig. 21, the larva in Figs. 5-16 and 22-27. the case in Figs. 1-4 and 31-34, and the pupa in Figs. 17-20 and 35 respectively.