Flowering cycles in the ‘Balami’ variety of Ficus sycomorus, the sycomore, were studied in connection with the sycophilous wasps Sycophaga sycomori and Apocrypta longitarsus. In the coastal plain of Israel the syconia of Ficus sycomorus may follow either of two developmental courses: most of the syconia swell rapidly, when still at an early stage of anthesis, thus producing genuinely ‘vegetative parthenocarpic’ fruit; some of them, however, become inhabited by Svcophaga sycomori and then follow a full developmental course, ultimately producing ‘stimulative parthenocarpic’ fruit. The latter type of fruit is seedless, as is the former, and the stimulus for its development is provided by the wasps ovipositing in the flower ovaries and by the subsequent activity of the wasp larvae within. In order to ascertain the reason for the absence of seeds, controlled pollination experiments were conducted. These experiments, and also systematic observations on the sequence of flowering generations throughout the year, have yielded information on seed-setting and the interrelations between the sycomore and its wasps.