Feeding responses by adult males ofMelanoplus sanguinipes(Fabricius) to carbohydrates and amino acids

Abstract

Adult males of Melanoplus sanguinipes (Fabricius), the migratory grasshopper, were starved for 18 h and were placed, one per arena, into arenas containing treated glass-fibre discs. The discs had been dipped into aqueous solutions of carbohydrates or amino acids of 0.0001, 0.001, 0.01, or 0.1 M concentration and allowed to dry at air temperature. They were placed vertically on pins and distributed at random among five equidistant stations around the periphery of the bottom of the arena. Each arena was provided with a glass-fibre disc that had been dipped in distilled water, as a control. The grasshoppers were allowed to feed at room temperature at 16:8 (L:D) for 24 h. Determinations of the effects of nutrient chemicals on feeding were determined by dry-weight differences between the weights of the treated discs before and after testing. Ribose, glucose, mannose and trehalose had no influence on feeding; 0.01 M fructose of 0.1 M arabinose, galactose, melibiose or sucrose increased feeding over that obtained with the control discs (P = 0.05); and 0.01 M xylose or sorbose depressed feeding. Each of the 11 amino acids investigated was phagodeterrent to adult males of M. sanguinipes. The present results confirm the variability of responses to carbohydrates among acridids; however, the reversal of phagodeterrency of sorbose or xylose at 0.1 M concentration is believed to be the first reported instance of such behaviour. In contrast to other reports of phagostimulation of acridids by individual amino acids or amino-acid mixtures, all protein amino acids tested in the present study were phagodeterrent to adult males of M. sanguinipes, even at low concentrations.