Movement behavior immediately before a jump in an experimental arena was investigated for 17 species, representing three central European grasshopper families (Caelifera). It was found that pygmy grasshoppers (Tetrigidae) execute quick forward and backward and occasionally sideways rocking movements, whereas acridids (Acrididae) and catantopids (Catantopidae) execute slow side-to-side movements. All movements are executed without locomotion and are limited to the horizontal plane. Six movement variations were observed for each of the three families; these were the same for the acridids and catantopids. Differences in the frequency of the movement variations and in the velocity and amplitude of the movements indicate species-specific adaptations. Because the movements are translatory and are oriented toward contrast boundaries, they can be regarded as peering motions. In acridids and catantopids, it can be assumed that image displacement is used for the determination of the jump distance. Jumps executed by pygmy grasshoppers were less accurate. Possibly the more irregular rocking movements of these ground-dwelling grasshoppers do not permit such accurate distance estimation as the slower side-to-side movements of the other species, but rather they serve to aid in overall perception of obstacles in the environment, for example. Because pygmy grasshoppers are considered to be more primitive than the other two families, their peering-jump behavior may provide indications concerning the evolution of peering movements. In grasshoppers, it seems that quick rocking movements evolved earlier than slow side-to-side peering movements. It seems plausible that the movements developed from locomotory and compensatory movements preceding jump takeoff.
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Vol. 102 • No. 2