THE SUBSPIRACULAR GLANDS OF HYALOPHORA CECROPIA (L.) (LEPIDOPTERA:SATURNIDAE): HISTOLOGY AND CYTOLOGY

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Abstract
A histological and cytological study of the subspiracular glands of the giant silkworm Hyalophora cecropia is reported. These glands are true organs, situated in the first eight abdominal segments, one gland under each spiracle. The glandular tissue is made up of extremely large cells varying from 15 to 25 μ by 8 to 18 μ in the first instar, and from 150 to 600 μ by 60 to 150 μ in the fifth instar and pupa. A cellular sheath encloses the glands in the later instars. Many tracheoles penetrate this sheath and disperse among the glandular tissue.The glands appear to secrete before each larval molt, before and after pupation and after the breaking of diapause in the pharate imago. After the last secretion the cells break down. All secretions are preceded by an enlargement of the nucleus in the earlier instars and by a profuse branching of the nucleus in the later instars. A nucleolus is observed prior to, and during each secretion, except for the secretions before and after pupation. The secretion appears to begin in the nucleus and extend through the cytoplasm to the blood. In the later larval instars, the gland cells increase in number by means of amitotic division.A comparison of this study with the literature makes it possible to conclude that in all holometabolous insects, a glandular structure can be found which is homologous to the subspiracular gland of Lepidoptera.A brief description of the subepidermal glands of Hyalophora is given to illustrate the distinction between the subepidermal gland cells which are often given the name oenocytes and the subspiracular gland cells which also have been called oenocytes.

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