The Senegalese grasshopper Oedaleus senegalensis is periodically a major pest of millet and other crops of subsistence agriculture in the Sahel zone of West Africa. Aspects of the species' biology are described. Eggs can survive several seasons and adults sometimes migrate up to 350 km per night, adaptations that contribute to the species' success in semi-arid areas. Evidence for migrations, both northwards with the S.W. monsoon and southwards with N.E. harmattan winds, is reviewed with particular reference to studies in Mali and Niger. Control strategies such as monitoring migrations and egg-laying to predict the sites of future outbreaks, possibly up to three years after heavy infestations, are considered.