A novel host-parasitoid association: first record of Nasonia vitripennis (Walker, 1836) (Hymenoptera: Pteromalidae) parasitizing Microcerella halli (Engel, 1931) (Diptera: Sarcophagidae) in southern Brazil

Records of trophic associations between sarcophagid flies (Diptera: Sarcophagidae) and their natural enemies remain scarce, limiting ecological and forensic interpretations of decomposition systems. Microcerella halli (Engel, 1931) is a Neotropical sarcophagid species of recognized relevance in carrion succession, yet its interactions with pupal parasitoids are poorly documented. Nasonia vitripennis (Walker, 1836), a cosmopolitan pteromalid and a key model in evolutionary ecology, parasitizes a broad range of dipteran hosts but has never been recorded from M. halli. Here, we report the first confirmed instance of N. vitripennis parasitizing M. halli, based on material collected in southern Brazil. From 178 puparia, 43 were parasitized by Nasonia vitripennis, yielding a total of 780 emerging adults. Mean brood size was 17.5 ± 9.2 individuals per parasitized puparium, calculated based on individual offspring counts per host. The emerging population exhibited a strongly female-biased sex ratio (5.78:1), and the proportion of females varied markedly among puparia (33.3–100%; mean = 85.2%). Emergence occurred within 24 days after collection under mean ambient temperature of 16.6 °C. This new association expands the known host range of N. vitripennis and underscores its reproductive efficiency as a gregarious parasitoid. Given the forensic value of M. halli, the presence of an efficient pupal parasitoid may affect population dynamics in carrion environments and offers perspectives for studies on host suitability, clutch allocation, and parasitoid performance in Neotropical systems. These findings highlight M. halli as a promising experimental host for behavioral and physiological investigations involving N. vitripennis.