The neuroendocrine system of Hyalophora cecropia (L.) (Lepidoptera: Saturniidae): I. The anatomy and histology of the ecdysial glands

The ecdysial (prothoracic) glands of the silkmoth, Hyalophora cecropia, were examined anatomically and histologically during the fourth and fifth larval instars and in the pupal and adult stages. Female gland cells were larger and, unlike those of males, usually contained prominent nucleoli. All gland cells were characterized by a peripheral “striated border” that appeared to be an area concerned with the release of the secretory product. Complete degeneration of the glands occurred shortly after adult emergence. The innervation of the glands is described, and the possible significance of this innervation is discussed. Cycles of activity, characterized by nuclear alterations that preceded cytoplasmic vacuolization, were correlated with the initiation of molting activity in each stage. In addition, secretory activity appeared to occur at a low level in young pupae and at higher levels in older pupae. The histological variations occurring in the gland cells during any single molting cycle were similar to, but not exactly duplicated by, those occurring in any other cycle. These latter findings suggested an alteration in the glandular control system during the several cycles examined.