Arrest of adult development in debrained pupae of the silkworm, Bombyx mori

The occurrence of developmental arrest after brain removal in pupae of Bombyx mori was examined using a racial hybrid Chinese No. 115 × Japanese No. 122. The results are as follows: (1) Adult development was blocked for a long period in most insects debrained shortly after larval-pupal ecdysis; (2) the earlier the brain removal, the more arrested pupae were obtained; (3) the critical period of brain hormone secretion for adult development was earlier in the female than in the male; (4) the developmental arrest which had been induced in female pupae tended to terminate earlier than that in males; (5) the developmental arrest which was induced by extremely early brain removal terminated earlier than that obtained by later brain removal.