Insect Migration has three main groups of chapters. The first and largest group describes insect migration in relation to weather and climate, with one or more chapters on Africa and Europe, North America, eastern Asia, and Australia. In West Africa seasonal reversal of windborne migration has been demonstrated for bugs, moths, and flies as well as several species of grasshoppers. Much migration in Africa is more complex and involves seasonally changing wind patterns in area of shifting habitat suitability. Their movements cannot be simply summarized, and there is no easily grasped return of migrant genes from their source areas.
Some migrations are fatal, with insects carried into deserts, poleward in autumn, and out to sea.
Yet staying put does not insure survival either. Passage of successive fronts may be required for migrants to reach overwintering areas. Two planthoppers in eastern Asia migrate northward and northeastward in spring and summer attacking rice in areas where they cannot overwinter. Some migration to the southwestward in autumn has been detected, but whether these are significant contributors to the gene pool of individuals that move northeastward the following year is uncertain. In China there seems to be enough return migration to make the northward migrations adaptive.