Grasshopper and Locust Pests in Australia

In Australia (also in Asia, Africa, and South and Central America), some grasshoppers (Orthoptera: Acrididae) are called “locusts.” This designation is applied to species of grasshoppers that display phase change. Phase change is largely a behavioral change between different states, gregarious and solitary forms. During the gregarious phase, which is induced by high densities, locusts tend to disperse long distances as groups (during the nymphal stage, the aggregations are called bands, during the adult stage, they are called swarms). These same species are not very dispersive or gregarious during the solitary phase. Physical changes in appearance may also occur during the change in phase, and of course physiological changes underlie the behavioral and morphological shifts. Transition between the solitary and gregarious phase takes more than one generation. In contrast, grasshoppers tend not to disperse long distances, tend not to aggregate during dispersal, and their appearance...