Changes of protein and nucleic acid synthesis in the developing colleterial glands of the silkmoth, Bombyx mori. To elucidate no-production of glutinous substance in the colleterial glands of Ng-mutant, Bombyx mori. Changes of the contents of protein and nuc1eic acid (RNA and DNA) and the activities of protein and RNA synthesis in the colleterial glands during pupal development were investigated. In the colleterial glands of Ng-muntant, the protein content increased very slightly during pupal development, whereas in normal the content increased lineally. The activity of protein synthesis in Ng-mutant was the highest at 5 day of pupal stage, and then deminished gradually through pupal development. In contrary to Ng-mutant, the activity in normal was enhanced through pupal development. RNA content of Ng-mutant was the highest at 5 day on pupal stage and decreased for pupal development, while that of normal was the same content as that of Ng-mutant at 5 day, reached the maximam content at 7 day pupa and then decreased. The activity of RNA synthesis of Ng-mutant was the highest at 5 day pupa and diminished during pupal development, on the other hand, that of normal was the same tendancy as that of Ng-mutant, but always the activities were higher than those of Ng-mutant. We confirmed autoradiographically that Ng-mutant is not able to synthesize glutinous proteins. Therefore, this suggests that no mRNA synthesis for glutinous protein may occur to the Ng-mutant.