The author has performed anatomical and histological observations on the morphological changes of the dermal glands during pupal moulting. For the histological observation the glands were fixed in GILSON'S and BOUIN'S fluids and sectioned by ordinary paraffin method for MALLORY'S triple stain. For the histochemical observation they were fixed in 95 per cent alcohol for UNNA-PAPPENHEIM'S pyronin-methyl green stain and in CARNOY'S fluid for FEULGEN reaction, and for the detections of PNA and DNA POLLISTER & RIS'S (1947), and SHIBATANI'S (1949) methods were employed.<br>1. The alveolar type dermal glands are observed in the 5th instar larvae as well as in the 4th instar larvae. Each cytoplasm in the secretory cells in the dermal glands locating from the first thoracic segment to sixth abdominal segment is filled with plenty of alveoli in the pre-pupal stage (PL. I, 7, 8. PL. II, 1, 2).<br>2. The granular type dermal glands in the 4th instar larvae locate in each segment, from the seventh abdominal to the ninth. During the 5th instar larvae, degeneration of the glands, in which the blood cells are concerned, is observed. They disappear from the end of the first about quarter of the per-pupal stage (PL. II, 3∼6).<br>3. The alveolar type dermal glands in the 5th instar larvae can be distinguished into two types, coloured and non-coloured. The former is yellow in colour, acidphile and shows a strong positive reaction of protein and contains agglutinate substances in each alveolus (PL. II, 1). The latter is opaque, non-coloured, basophile and shows a weak positive reaction of protein and contains a few agglutinate substances in each alveolus (PL. II, 2). The glands located in all thoracic segments and the first abdominal segment belong to the coloured type, while those located in each segment from the second abdominal to the sixth belong to the non-coloured type. In the 4th instar larvae, the glands of alveolar type located from the first thoracic segment to the sixth abdominal one are colourles, while those of the granular type are yellow in colour. These facts appear to show that glands of the coloured type in the 5th instar larvae have the same characters, i.e., the colour, the stainability and the positive protein reactions of the secretory cell, as those of the granular type in the 4th instar larvae.<br>4. The alveoli in the secretory cell grow in number step by step with age (PL. I, 1∼8). The contents in those alveoli are secreted in the space between the old and new layers of cuticle at the pupal moulting.<br>5. The histochemical changes with age of PNA and DNA in the dermal glands during the 5th instar larvae are the same as in those during the 4th instar larvae.