Abstract: Bactrocera cucurbitae and B. tau are sibling species. They often occur in mixed populations in the field and are difficult to control. To clarify the oviposition patterns of those two species, we cultured them in artificial climate chambers. We measured oviposition status and oviposition duration, and analyzed the correlation between age and fecundity. The results showed that the average adult longevity and oviposition period of B. cucurbitae adults were 78.83 and 61.47 days, respectively, being shorter than those of B. tau (94.77 and 75.33 days). The average number of eggs laid per female per day and the average number of egg clutches per female per day were 10.64 and 8.83 for B. tau, which were higher than those of B. cucurbitae (6.57 and 6.56, respectively). The total oviposition period of B. tau was 4 days longer than that of B. cucurbitae, and its cumulative average fecundity reached 625.87 eggs, approximately 200 more than B. cucurbitae (431.41 eggs). These findings suggest that B. tau exhibits a stronger oviposition competitiveness under indoor conditions. Therefore, in field management, effective control measures should be implemented before oviposition, with differentiated strategies for species-specific outbreaks. Priority should be given to targeting the more harmful species, while the other should be managed accordingly.

Key words: Bactrocera cucurbitae, Bactrocera tau, oviposition period, fecundity, interspecific competition