INSECT MIGRATION - VARIABILITY AND SUCCESS IN A CAPRICIOUS ENVIRONMENT

Stochastic effects of climate and weather have a pervasive influence o n the induction, performance and evolution of migration. In wing-dimor phic species, their influence on habitat quality, and on rates of deve lopment of the migrant itself, maintains variation in responses to env ironmental cues determining wing-form and migratory behaviour. Migrant s flying above their flight boundary layer rely on winds to disperse t hem across landscapes in which their habitats are distributed. Pattern s of distribution of habitat patches, and the influence of changing wi ndspeeds and direction on the displacements of migrants, result in sel ection for variation in migratory potential at each migration. In subs equent migrations, this variation and stochastic effects of the winds on groundtracks of individual migrants ensure that their destinations 'sample' the landscapes they travel over. The extent and resolution of this sampling, by which migrants reach favourable habitats, depend on the components of migratory potential, their mode of inheritance, and genetic correlations between them, as well as on the characteristics of the winds on which they travel.