Abstract: 【Aim】 Aenasius bambawalei (Hymenoptera: Encyrtidae) is an accompanying parasitoid of the invasive mealybug, Phenacoccus solenopsis (Homoptera: Pseudococcidae), and it was known that this parasitic wasp only parasitizes the mealybug. However, we newly discovered that A. bambawalei can parasitize another alien invasive mealybug, P. solani (Homoptera: Pseudococcidae), in China. This study aims to determine the fitness of A. bambawalei on the new host species, so as to provide a scientific basis for the full development and utilization of the parasitoid in the future. 【Methods】 The fitness of A. bambawalei on P. solani of different developmental stages with potato as the host plant was determined in the laboratory, and the formation time of mummies, emergence time, longevity, hind tibia length, parasitism rate, emergence rate and offspring sex ratio of A. bambawalei adults on the above two host species under non-selective conditions were also investigated. 【Results】 A. bambawalei parasitized the female adults and the 2nd and 3rd instar nymphs of P. solani, but only emerged from the parasitized female adults. The most appropriate parasitiod-host ratios were 2∶15 and 2∶20 with P. solenopsis and P. solani used as the hosts of A. bambawalei, respectively. Host species showed no significant influence on the formation time of mummies and the emergence time of A. bambawalei, but significantly influenced the longevity of A. bambawalei. The longevity of A. bambawalei adults emerged from P. solenopsis was ca. 20 d longer than that emerged from P. solani. Moreover, the parasitism rate of A. bambawalei on P. solenopsis was higher than that on P. solani (54.0% vs. 25.3%), but the emergence rates of A. bambawalei on the two hosts showed no significant difference (both over 90%). The proportion of female wasps emerged from P. solenopsis was higher than the proportion of female wasps emerged from P. solani. 【Conclusion】 A. bambawalei can parasitize female adults and the 2nd and 3rd instar nymphs of P. solani, but only completes generation development on its female adults. A. bambawalei on P. solani shows a disadvantage in the longevity and individual female size compared with that on the more suitable host P. solenopsis.

Key words: Aenasius bambawalei, Phenacoccus solenopsis, Phenacoccus solani, host suitability, alien invasive species, biological control