1. Fig trees (Ficusspp.) and their host‐specific pollinator fig wasps (Agaonidae) are partners in an obligate mutualism. Receptive phase figs release specific volatiles to attract their pollinators, and this is generally effective in preventing pollinator species from entering figs of the wrong hosts.2. If entry is attempted into atypical host figs, then ostiole size and shape and style length may also prevent reproduction. In spite of these barriers, there is increasing evidence that fig wasps enter atypical hosts, and that this can result in hybrid seed and fig wasp offspring.3. This study examines the basis of pollinator specificity in two dioecious fig species from different geographical areas.Kradibia tentacularispollinatesFicus montanainAsia.Ficus asperifoliafromEastAfrica is closely related but is pollinated by a different species ofKradibia.4. In glasshouses,K. tentaculariswas attracted to its normal host,F1sand backcrosses, but only rarely entered figs ofF. asperifolia. Foundresses were able to lay eggs in hybrids, backcrosses, andF. asperifolia, although flower occupancy was lowest inF. asperifoliafigs and intermediate in hybrids.5. The fig wasp failed to reproduce in femaleF. montana,maleF. asperifolia, and maleF1s, and most but not all backcrosses toF. montana.This was a result of the failure to initiate gall production.6. Host specificity in this fig wasp is strongly influenced by host volatiles, but the ability to gall may be the ultimate determinant of whether it can reproduc