The acridoid grasshoppers in general and the various species of swarm-forming locusts in particular have been among the most favoured subjects of insect physi- ology, behaviour and ecology for many years. Several factors contribute to this popularity: their abundance in nature and their ease of culture in the laboratory, their relatively large size, and most of all, perhaps, their agricultural importance and the consequent intermittent availability of funds for their study. These factors together have inspired a large amount of experimental work, and this in tum has produced a new and often...