DISPERSAL OF ADULT FEMALE FIG WASPS .2. MOVEMENTS BETWEEN TREES

Fig wasps (Chalcidoidea, Agaonidae, Agaoninae) are the exclusive polli nators of fig trees (Ficus spp., Moraceae). Fig development on the Afr ican fig tree, F. burtt-davyi, is normally synchronised on individual trees, but not between trees. Consequently the females of each generat ion of the pollinating species (Elisabethiella baijnathi) have to disp erse to other trees to find 'receptive' figs which are suitable for ov iposition. This paper examines this aspect of fig - fig wasp biology. The flight speed of insects is closely linked to their size, and direc tional flight is difficult for small insects, such as fig wasps, in al l but the lightest of winds. We investigated the movements of fig wasp s between trees using sticky traps placed around fig trees or near cot ton bags containing figs. Away from the trees, the densities of flying wasps at different heights was also determined. When the wasps disper se from their natal figs they take off near-vertically. They are unabl e to exert directional control once they enter the air column and are subsequently blown downwind. Near receptive host trees the wasps appea r to lose height and then Ay upwind at speeds of around 25 cm/sec.