Biology of the parasitoid Melittobia sosui Dahms, 1984 (Hymenoptera: Eulophidae) with details on its ecology, development, and reproduction in Vietnam

In this study, we determined the total developmental time of Melittobia sosui Dahms from the egg to the emergence of imagoes being 12.7–30 days for males and 14.7–34.6 days for macropterous females. Its developmental time depended on the laboratory temperature and humidity. Based on tests of the developmental time through 23 months from 2019 to 2021 and field-collected data, it is concluded that Melittobia sosui is active throughout year except for its pupal diapause lasting 2–3 weeks during the winter. The average life cycle was 23 ± 7.5 days. Males did not feed after emerging and lived from 6.5 to 8.2 days. Females feeding on host hemolymph had a life span from 29.2 to 42.2 days depending on the room temperature and humidity. The number of offspring produced depended on the host quality and varied from 65.6 to 145.4 individuals per foundress. Related to host weights, Melittobia sosui held an offspring clutch size of about 2.6 individuals per mg of Chalybion malignum (Kohl) and about 1.6 individuals per mg of Chalybion bengalense (Dahlbom) and of Sceliphron madraspatanum kohli Sickmann (three, Sphecidae). Regardless of the laboratory temperature and relative humidity, but depending on the host quality (different hosts), the sex ratio varied from 0.96 to 0.98, the average female-dimorphism ratio was 0.99 ± 0.01 and the mean developmental mortality rate of pupa was 0.92 ± 1.78%. Our findings provide a better understanding of the biology and ecology of Melittobia sosui and contribute to devising suitable control measures for the species.