The Occurrence of Mucoid Substances in Insects

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Abstract
Three histochemical tests, which demonstrate mucoid substances of vertebrate origin, have been applied to a variety of insect tissues. Mucoid materials seem to be absent from the contents of the insect midgut, but a positive reaction may be given by the striated border of the epithelium. Goblet cells of the larval midgut of Lepidoptera and rectal glands of all of the insects studied give a negative reaction, but the salivary glands of the cockroach, grasshopper, larval calliphorids, and worker honeybee all contain mucoid substances. In general, these materials seem to be of less frequent occurrence in insects than they are in most other animal phyla. The significance of the observed distr. of mucoid substances in insects is discussed, particularly in relation to the functions of the peritrophic membrane and the salivary glands.