ThelytokousWolbachia-infectedTrichogrammaspecies have long been considered as biological control agents against lepidopteran pests in agriculture and forestry.Wolbachiahas been suggested to increase the probability of the superparasitism ofTrichogramma, but the fate of infected offspring in the superparasitised host is still unknown. The present study aimed to evaluate the fitness of thelytokousWolbachia-infected (TDW) and bisexualWolbachia-free (TD)Trichogramma dendrolimiMatsumura (Hymenoptera: Trichogrammatidae) lines in superparasitised or single-parasitised hosts. The results showed that irrespective of whetherTrichogrammawasps were developed from superparasitised or single-parasitised hosts, the TDW line was characterized by reduced fitness, including lower fecundity, shorter longevity, and smaller body size of F1 offspring, and lower emergence rate of F2 offspring than the TD line. This was not true for the survival rate and developmental time of F1 offspring. Additionally, the fitness parameters ofT. dendrolimithat developed from superparasitised hosts were lower compared with that ofT. dendrolimithat developed from single-parasitised hosts. Interestingly,Wolbachia-infected females had higher dispersal capacity than bisexual females when they developed from superparasitised hosts. The results indicated thatWolbachianegatively affects fitness ofT. dendrolimi, but enhance dispersal capacity ofT. dendrolimifemales in superparasitism condition. Further studies need to be carried out to select the best line that will allowWolbachiaand their hostTrichogrammato be better adapted to one another.

The endosymbiotic bacteria, Wolbachia , live widely within cells of arthropods. Wolbachia are not only transmitted vertically from host mother to offspring, but are also transmitted horizontally among host individuals. Horizontal transmission is expected to occur during superparasitism when host parasitoid females deposit a clutch of eggs on a host previously parasitized by the same parasitoid species.

ThelytokousWolbachia-infectedTrichogrammaspp. are widely used egg parasitoids against lepidopteran pests in biological control programs.Wolbachiamay manipulate host wasps for superparasitism and is sensitive to temperature. To explore effects of temperature and superparasitism, we compared fitness parameters andWolbachia-mediated phenotype of thelytokousWolbachia-infectedTrichogramma dendrolimibetween those emerging from superparasitised or single-parasitised hosts at 17, 21, 25, or 29 °C. Infected mothers ofT. dendrolimishowed reduced superparasitism and parasitism increased with temperature.Wolbachiatitre decreased with temperature when females emerged from singly-parasitised hosts, but there was no correlation in superparasitised hosts. Females showed higherWolbachiatitres at 21, 25, or 29 °C when developing from superparasitised hosts. The daily male ratio of offspring increased with temperature, and the day-age threshold for 5%, 50%, or 95% daily male ratio decreased with temperature in both parasitism forms. Females that emerged from superparasitised hosts had a shorter life span and reduced fecundity. These results indicate thatWolbachiamay affect host behaviour by increasing superparasitism to enhance its spread, but this has negative effects on thelytokousWolbachia-infectedT. dendrolimi.