THE INTERCEREBRALIS-CARDIACUM-ALLATUM SYSTEM OF SOME PLECOPTERA

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Abstract
The histophysiological study of the intercerebralis-cardiacum-allatum system in 21 species of Plecoptera, resulted in the following observations: From the anatomical point of view, the type of Chloroperla (Hanstrom, 1940) characterized by paired symmetric corpora allata, exists in the Perlodidae, Perlidae, and Chloroperlidae. The type of Nemura. characterized by an unpaired, laterally located corpus allatum, corresponds to the Nemuridae, Leuctridae, and Capniidae. A 3d anatomical type of which an unpaired but definitely medial corpus allatum is typical (type of Brachyptera) exists among the Taeniopterygidae. The cells of origin of the nervi corporis cardiaci I of the Plecoptera possess all the morphological characteristics of neurosecretory cells. Their secretory product is stainable with acid dyes, azocarmin, iron hematoxylin, and chrome hematoxylin. This secretory product migrates along the axons and accumulates between the cells of the corpora cardiaca. These elaborate a secretory product of their own which stains with the phloxine of the method of Gomori. The neurosecretory product migrates along the nervi corporis allati and occurs between the cells of the corpora allata; one also encounters it in the nerves which run from the corpora allata to the prothorax in the Plecoptera of the Chloroperla type. The secretory activity in the cells of the pars inter-cerebralis is at its peak towards the middle of the larval period; the phenomena of neurosecretion are less pronounced in the later stages of larval life and in the imago. The corpora cardiaca and allata reach their maximal volume in larvae which are still a considerable period away from the imaginal molt. In the later stages of post-embryonic development atrophy of the endocrine glands of the head region is observed. This mode of development is different from that described in other insects belonging to the Neoptera; it must be understood in relationship with the peculiar chronology of the neurosecretory activity in the Plecoptera.