Abstract: A laboratory research aimed at determining the stimuli used by adults Psyttaliaconcolor in order to locate the microhabitat (fruits) of its tephritid host Ceratitis capitata wasperformed. Experienced mated females of P. concolor were used in two-choice biossays in a stillairarena, by employing two different fruits (apple and peach), uninfested or infested byC. capitata larvae. Results showed that uninfested fruits were significantly attractive to femalesthan odourless control (artificial fruit). Infested fruits were significantly chosen instead ofuninfested fruits, so indicating the ability of females to readily discriminate differentquantities/qualities of stimuli due to host infestation. When infested fruits were offered incomparison to infested fruits in which larvae were removed immediately before test, parasitoidfemales significantly chose the first stimulus. Therefore, the optimal response of P. concolor inhost finding behaviour has been achieved when a complex of both chemical (i.e. volatilesderiving from host-infested decaying fruits and from the host itself) and physical (i.e. hostinducedvibrations by feeding or moving) stimuli were simultaneously offered to the females.