Abstract
Neurosecretory cells in the brain of Pieris rapae crucivora were observed electron microscopically when the incidence of pupal diapause was determined humorally. Four types of NSC (neurosecretory cell) were classified according to the features of cell structure, i.e. cell size, evagination of glial cells into NSC, endoplasmic reticulum, golgi body, and especially, size of the secretory granules. There were two NSC-I's containing secretory granules of ca. 100mμ in diameter and about ten NSC-II's with 220-240mμ secretory granules in the dorsal part of the pars intercerebralis. And there were two NSC-III's with 180-350mμ secretory granules in the frontal part of the pars intercerebralis and several NSC-IV's with ca. 120mμ and larger secretory granules in the dorsolateral part of the brain. NSC-II's were presumed to be the source of the brain hormone (thoracotrophic hormone), because remarkable differences in cell activity were observed between diapause individuals and the non-diapause ones.
