SOME HISTOCHEMICAL CHARACTERISTICS OF TISSUES IN LARVAE OF CTENICERA DESTRUCTOR (BROWN) (COLEOPTERA, ELATERIDAE), WITH SPECIAL REFERENCE TO CUTANEOUS SENSILLA

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Abstract
The sensory axons from the cutaneous sensilla and some of those in the recurrent nerve stain strongly with S-specific stains. The axons of the efferent system and those from the ocelli lack this staining characteristic. This difference among axons possibly is related to the origin of their precursors in the ontogenetic sequence.Some of the metabolites involved in the synthesis of cuticular structures are demonstrated and discussed. The following sequence in the synthesis of the cuticula is suggested: glycogens → more complex, diastase-fast polysaccharides → chitin → a carbohydrate–protein complex containing SS groups → a complex (procuticle) with potential SH groups → a complex (exocuticle) with bound S and a high content of tyrosine and other phenols. The sequence in the synthesis of the cuticular nerve sheaths appears basically similar. The last step was not evident in tonofibrillae, and the last two steps were not evident in the subcuticular sheaths or axoplasm of reactive axons.The mechanisms of the histochemical reactions are discussed, with particular reference to staining with aldehyde-fuchsin after oxidation with potassium permanganate. This method may serve to differentiate histologically certain afferent from efferent axons in insect nervous systems.