The neurosecretory cells and retrocerebral endocrine glands of Amsacta collaris Hampson (Lepidoptera: Arctiidae) during post-embryonic development.

Neurosecretory cells and retrocerebral endocrine glands of Amsacta collaris Hampson have been studied by using PF and PARF techniques in whole mounts and sections. On the basis of staining properties, three principal types of cells viz., A, B and C-types have been distinguished, which have been further classified into A-1, A-2, A-3, A-4, B-1, B-2 and C-1, C-2 subtypes respectively. The cells are arranged in 12-groups i.e. 2-medial, 2-lateral, 2-optic, 2-posterior, 2-ventral and 2-tritocerebral. The material elaborated in the medial, lateral, ventral and posterior groups of cells is stored in the outer part of the corpus allatum and that of the optic and tritocerebral, is stored in the corpus cardiacum. In addition to brain, distinct neurosecretory cells have been observed in the frontal and hypocerebral ganglia, and in the latter case they have been reported here probably for the first time in Lepidoptera. The corpora cardiaca are a pair of club-shaped or stellate bodies lying behind the brain, with which they are attached by NCC-I and NCC-II. The corpora cardiaca are composed of only a few intrinsic cells. Some nerves arise from the corpus cardiacum and innervate the gut dialator muscles, recurrent nerve, aorta and the adjacent organs. The corpora allata are oval in shape, attached to the corpora cardiaca via allatic nerve. In larval stages, each corpus allatum is a single lobed body which becomes many lobed in late pupa and adult stages. The gland is superficially innervated by the neurosecretory axons of cerebral origin which contain a large amount of NSM. Thus the outer part of the gland acts as a principal neurohaemal organ. The inner part of the corpus allatum is devoid of NSM.