Locust displacing winds in eastern Australia

Abstract

In interior eastern Australia, adults of the Australian plague locust with substantial fat reserves migrate down-wind on warm nights if there has been a strong surface wind during the day; limited dispersion occurs with all adult infestations and requires only that the sunset temperature be above the flight threshold. The frequencies of the 900 mb wind, which is near the locust's flying height, from different directions on nights suitable for either mass migration or limited dispersion, have been found for representative months. These differ from the frequencies for all nights in the southern parts of the area, especially in the spring and autumn, since winds are generally warmest from the north. Northerly and westerly locust displacements should occur frequehtly except in the extreme south. Such movements have been observed only rarely. Nevertheless upsurges in the remote interior, where most major plagues start, may be followed by abortive migrations to the desert areas further west as often as by invasions of the farming belt to the south and east.