The effect of haemolymph osmotic pressure on the meal size of nymphs of Locusta migratoria L.

Injection of trehalose into the haemolymph of Locusta nymphs reduced the amount of grass eaten in one meal. Greater effects were produced by higher concentrations and most reduction occurred when meals began 20 min after injection. Sodium chloride, glycine, proline, sorbose, inulin or a mixture of solutes had similar effects. The similarity of effects is explicable in terms of the increase in haemolymph osmotic pressure. The increase in the osmotic pressure normally occurring during feeding is not great enough to affect the current meal.