In this study, we assessed the reproductive output and sexual dimorphism in body size as well as nine other morphometric variables of Abscondita chinensis and Abscondita terminalis collected from Lishui (Zhejiang, eastern China) during their breeding seasons. The results of two-way ANOVA analysis revealed that A. chinensis had significantly greater total length than A. terminalis, and females exhibited significantly larger total length compared to males. A two-way ANCOVA was conducted with total length as a covariate, followed by Tukey’s test, which revealed that the pronotum width, elytron length, compound eye width, thorax length, abdomen width, photogenic organ area, and body weight of A. chinensis were all significantly smaller than those of A. terminalis. Additionally, the abdomen length of A. chinensis was significantly larger than that of A. terminalis while there was no significant difference in antenna length between the two species. Females exhibited significantly greater pronotum width, abdomen length, abdomen width, and body weight compared to males, while their elytra length, compound eye width, thorax length, antenna length, and photogenic organ area were significantly smaller. The interaction between species and sex had significant effects on pronotum width, compound eye width, abdomen length, antenna length, and photogenic organ area; however, no significant effects were observed on elytron length, thorax length, abdomen width or body weight. The sexual dimorphism indices of A. chinensis and A. terminalis gradually approached 0.144 and 0.091, respectively. The principal component analysis (with eigenvalue ≥ 1) of the nine morphological variables revealed that the first two principal components accounted for a total variation of 56.8%. In the first principal component, compound eye width and photogenic organ area exhibited higher negative loading coefficients, while abdomen length showed a higher positive loading coefficient (explaining 31.3% of the variation). The second principal component had high negative loading coefficients for pronotum width and elytron length (explaining 25.5% of the variation). The mean clutch size of A. chinensis and A. terminalis was 28.9 and 18, respectively. Linear regressions examining the relationship between reproductive output and maternal individual size revealed significantly positive correlation between clutch size and both maternal total length and body weight. The results of one-way ANOVA indicated that A. chinensis individuals with specific total-length laid significantly higher number of eggs compared to those of A. terminalis. Both A. chinensis and A. terminalis exhibited female-biased sexual size dimorphism, which is the result of a combination of fertility selection, energy allocation, and movement. The increase in key local features such as ventral volume in female flies represents an adaptation to fertility selection, and the degree of heteromorphic variation between sexes is positively correlated with species fertility.