FLIGHT BEHAVIOR OF RHAMMATOCERUS SCHISTOC ERCOIDES (REHN, 1906) SWARMS IN THE STATE OF MATO-GROSSO IN BRAZIL (ORTHOPTERA, ACRIDIDAE, GOMPHOCERINAE)

Flight behaviour study in Rhammatocerus schistocercoides swarms in the state of Mate Grosso, in Brazil, shows that this specie has a limited dispersal ability, in opposition to previous hypothesis. Several swar ms have been studied daily, at one minute intervals. The distance cove red in one day by swarm displacements is only of a few hundred meters, even in favorable thermal conditions. The largest daily displacement observed was of 2.5 km. Swarms have a classical << rolling >> behaviou r; numerous individuals roost on the ground as the others are in fligh t. Each day, if the temperature is sufficient, the take off seems syst ematic, whatever the biotope, favourable or not. The height of flight is low and does not exceed 5 to 10 meters. Their direction is mainly d etermined by the wind. Flight activity seems maximal during sexual mat uration; it stops temporarily during oviposition. These local migrator y movements enable the swarms to widely explore their environment (sav anna and tree savanna areas) during the dry and generally unfavourable season. The regular eastward migration of this gras shopper - hypothe sis regularly put forward during the last ten years - seems completely impossible given its flight behaviour and local aerologic characteris tics.