Field cage studies were conducted in Reunion Island in order to determine the optimal age for mating in the local wild Ceratitis capitata and Ceratitis rosa strains. A standard methodology, as defined during the second Research Coordination Meeting, was used during these studies. In C. capitata, we recorded a higher proportion of 9 days-old (45 %), then 7 days-old males in the observed pairs. We also observed a higher proportion of 9 days-old females in the formed pairs (58%), followed by 7 days-old females (34%). Female choice did't seem to be much afiected by its age : 9 or 7 days-old females showed a slight preference for 9 days-old males, followed by 7 days-old males. The relative proportion of the various ages confirm that, in the conditions of our experiment, males require a shorter maturation period before they are able to mate successully. In our climatic conditions, the higher number of pairs was collected in the morning at 8 and 9.00 a.m. With C. rosa, a first experiment with individuals of the same ages as C. capitata (3, 5, 7 and 9 days) gave negative results. A second experiment was done using flies of 11, 13, 15 and 17 days. We recorded a higher proportion of 13 days-old males (37 %,), then 17 days-old (25%), 15 days-old (20 %) and 11 days-old (18%) in the formed pairs. For females, we recorded a higher proportion of 15 days-old (35%) and 13 days-old (33 %) individuals. Females of the fist three age classes showed the same préférence for 15 days-old males. In this species, the great majority of the pairs was observed at the end of the afternoon, at 6.30 and 7.00 p.m. These results will be helpful for video recordings of the mating behaviour that are currently in progress.