The thesis embodies the histomorphological changes in the numbers, types, groupings and secretory cycles of neurosecretory cells of the brain of Prodenia litura, particularly pupal period. In the development of a Lepidopteran, the major stages are the larvae, prepupa, pupa and adult. Pupation is the crucial period wherein maximum changes take place for transformation of a larva into an adult. The numbers and arrangement of neurosecretory cells in the larval brain are quite distinct from those in the adult brain of Prodenia litura. During pupation period, transition of neurosecretory sysem of larval brain to adult brain has been studied. During larval period fully formed neurosecretory cells are observed in a 5th instar stage, but gradually they get modified and transformed during inactive larval, prepupal and pupal stages into neurosecretory cells of the adult. Therefore, extensive studies on neurosecretory cells of the brain have been made at specific intervals of all stages, viz., active larva, fully fed inactive larva, prepupa and pupa. Fully formed neurosecretory cells of adult have been studied in just emerged adult.