Diet breadth and anti-predator strategies in desert locusts and other Orthopterans

Abstract

Abstract A density-dependent change from a cryptic to an aposematic antipredator strategy has recently been suggested as a possible functional explanation for phase change in the desert locust (Schistocerca gregaria Forskal). Predators learn to avoid locusts that have fed on toxic plants faster when they are in the brightly colored gregarious phase than when they are green and solitarious. We review recent work comparing acquisition of a defensive compound via food selection between solitarious, transiens (solitarious locusts in transition to the gregarious phase) and gregarious locusts. Lab experiments showed that solitarious locusts were deterred at first contact with hyoscyamine, a plant compound that protects against predators, but later habituated to the compound and incorporated it into the diet (albeit at a low rate). By contrast, gregarious and transiens locusts fed readily on the compound. A computer simulation showed how low-density, solitarious locusts would not benefit much from consuming the ...