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The histochemical tests have been performed to evaluate the polysaccharide and protein contents of the salivary gland of three insects with different feeding habits. Aspongopus janus (Hemiptera), Laccotrephes maculatus (Hemiptera) and larval Euprotis scintillans (Lepidoptera). While the salivary content of E. scintillans includes both acid (AMPS) and neutral (NMPS) mucopolysaccharides, that of A. janus and L. maculatus has only AMPS. The AMPS of E. scintillans and A. janus contains sulphated groups, while that of L. maculatus has carboxyl groups, weakly and/or non-sulphated groups. The histochemical tests for protein reveal the presence of protein-bound--SS,--SH and--NH2 groups and tyrosine-containing protein in the salivary content of all the insects under study. Besides, arginine- and histidine-containing protein has been detected in the gland of A. janus. The possible physiological significance of these histochemical constituents of the gland has been discussed.

A histological and histochemical study of the ovary of Dysdercus koenigii has been carried out to ascertain the origin of protein, lipid and carbohydrate components of the yolk during vitellogenesis. Germaria of the telotrophic ovarioles of this insect comprise mononucleate and binucleate trophocytes, prefollicular cells and oogonia ensheathed in two membranes. The follicular epithelium derived from the prefollicular cells is multilayered in the beginning of the oocyte development but is progressively reduced to one layer in later stages. Chromatin material in the binucleate trophocytes condenses to form DNA-positive blobs. RNA-positive material flowing from the nutritive cords can be seen at the nutritive cord-oocyte junction. Protein bodies appear first in the intercellular spaces of follicular epithelium during the early vitellogenic stages indicating the supply of yolk protein from the haemolymph. Lipids originate as L1 bodies made up of unsaturated phospholipids in the nucleus (germinal vesicle). These bodies by addition of saturated triglycerides from haemolymph change to L2 bodies, which in turn, knock off phospholipid part and change of L3 bodies. Polysaccharides come as extrusions from the germinal vesicle while glycogen is first seen in the intercellular spaces of follicular epithelium and then passes into the oocyte indicating its origin in the haemolymph.