Abstract: Exploring the interspecific competition between Zeugodacus cucurbitae and Z. tau in larval stage on Cucurbitae moschata provides reference for understanding population dynamic, development and succession of these two pests in the field. C. moschata was selected as the host, and inoculated with different densities of Z. cucurbitae and Z. tau. The growth and development parameters (such as pupal duration) were measured under laboratory conditions, and the correlation among the parameters was analyzed. The results showed that Z. cucurbitae and Z. tau had similar density effect caused by the interspecific competition. With the increases of population density, both Z. cucurbitae and Z. tau exhibited prolonged pupal duration, reduced pupal weight, and eclosion rate. The pupal duration of Z. cucurbitae and Z. tau increased from 7.83 d and 8.01 d to 9.14 d and 9.31 d, while the eclosion rate decreased from 67.50% and 19.91% to 8.33% and 5.40% at each 60 larvae/10 g feed, respectively. There was a correlation among the growth parameters of Z. cucurbitae and Z. tau. Pupal duration was negatively correlated with other growth parameters. Pupal weight, eclosion rate, and sex ratio were positively correlated each other. With the increases of competition intensity, sex ratios of these two fruit fly species were decreased. The sex ratio of Z. tau was significantly positively correlated with pupal weight, but not for Z. cucurbitae. Z. cucurbitae had stronger anti-crowding ability and was more dominant in the interspecific competition with Z. tau when they coexisted on C. moschata.

Key words: Zeugodacus cucurbitae, Zeugodacus tau, interspecific competition, growth parameter