Objective To compare the differences of parasitism and progeny development of Sclerodermus alternatusi on different stages of Thyestilla gebleri.

Method The parasitism rate, developmental duration, female and male progeny number, male progeny proportion of S. alternatusi parasitized the larva and pupa of T. gebleri were investigated.

Result The results showed that both the larva and pupa of T. gebleri could be parasitized by the bethylid, and the parasitism rate on different stages of T. gebleri showed no significant difference. Successful emergence rate of parasitoid offspring showed significant difference on different stage of T. gebleri, 93.33% and 57.69% emergence rates were observed on the larva and pupa of longhorn-beetle. The pre-oviposition period of female wasp, egg stage, larval stage, pupal stage, and immature stage of wasps' offspring showed no significant differences on the larva or pupa of host, T. gebleri. The average pre-oviposition periods of female wasps were 6.63 d and 6.43 d when they were inoculated on the larva and pupa of cerambycid host, respectively. The average durations of offspring egg, larval, pupal, and immature stage were 4.34 d and 4.57 d, 8.34 d and 8.52 d, 19.89 d and 20.07 d, 32.61 d and 33.40 d, respectively. The number of female progeny and the total number of offspring were 39.50 and 41.18 when the parasitoid parasitized on the host larva, respectively; and the average numbers were 30.80 and 32.20 when the parasitoid were bred with host pupa. Both had significant differences. There was no significant difference in the number of male progeny when the foundress parasitized on host larva or pupa, with an average of 1.96 and 1.40. The male proportion was also not significantly different, with an average of 5.00% and 4.45%, respectively.

Conclusion Emergence rate and female progeny quantity of parasitoid parasitized the T. gebleri larva are much higher than the beetle pupa was used as host. Using the late-stage larva of T. gebleri as alternative host can result in the highest fitness in the mass-rearing of S. alternatusi.