THE NUTRITIONAL REQUIREMENTS OF GRASSHOPPERS: II. EFFECTS OF PLANT PHOSPHOLIPIDS AND EXTRACTS OF BRAN ON GROWTH, DEVELOPMENT, AND SURVIVAL OF THE GRASSHOPPERS MELANOPLUS BIVITTATUS (SAY) AND CAMNULA PELLUCIDA (SCUDDER)
Nymphs of the grasshopper Camnula pellucida (Scudder) were reared successfully to the adult stage on the chemically defined synthetic diet used for Melano-plus bivittatus (Say). Effects of wheat-germ oil, two fractions of wheat-germ oil (neutral lipid fraction and phospholipid fraction), and lecithins on growth, development, and survival of M. bivittutus and C. pellucida were studied. Experiments showing enhanced growth and development of both these species of grasshoppers, after the addition of phospholipid fraction of wheat-germ oil in the synthetic diet, were confirmed by incorporating commercially available phospholipids, as phosphatidyl serine and phosphatidyl inositol (which are constituents of wheat-germ oil), in the synthetic diet. As growth could occur on diets lacking special gustatory substances but containing only essential nutrients, the apparent improvements in growth and development of nymphs on diets containing phospholipids were attributed to enhanced palatability of the diet. The effects of higher moisture rontent available because of the use of different-sized cages for rearing were also demonstrated on both the species of grasshoppers. Higher relative humidity available in small plastic dishes improved growth and development of M. bivittatus nymphs, but these factors did not show any apparent effects on growth and development of C. pellucida nymphs. Ether extract of bran did not improve growth of either species, but ethanol extract of ether-extracted bran and ether-and-ethanol-extracted bran improved growth of both the species to a great extent. M. bivittatus could eat and grow from firat-instar nymphs to the adult stage on bran, whereas C. pellucida. nymphs could not grow and survive on bran alone. Behavioral differences of the two species of grasshoppers were discussed.