The functional significance of switching interval in food mixing by Locusta migratoria

To investigate the consequences of different patterns of switching between nutritionally complementary foods, nymphs of Locusta migratoria L. (Orthoptera: Acrididae) were forced to alternate between pairs of artificial foods differing only in their protein and carbohydrate content at one of several fixed intervals. Total food and nutrient intake over 6days were very similar in all groups despite the considerable variation in temporal patterns of nutrient intake. The effects of these treatments were determined using measurements of growth, stadium duration and carcass composition. Those given a low variance food pairing showed little effect in any of the measures while those given a high variance pairing showed no differences in dry weight growth or stadium duration but did differ in protein and lipid content. There was little evidence from our measurements that an ad-libitum alternation time of 4h previously observed in a laboratory experiment was physiologically optimal, suggesting that ecological factors may underlie such behaviour. Possible compensatory mechanisms used by L. migratoria are suggested.