Host adaptation of a gregarious parasitoid Sclerodermus harmandi in artificial rearing

Adaptations of a parasitoid, Sclerodermus harmandi (Buysson 1903) (Hymenoptera: Bethylidae) to a target host, Monochamus alternatus Hope (Coleoptera: Cerambycidae), were investigated in laboratory colonies. We quantified the physiological and behavioral flexibility of the parasitoid reared on M. alternatus compared to the parasitoid reared on a common host, Saperda populnea (Coleoptera: Cerambycidae). Adult performance (fecundity and pre-oviposition period) and offspring physiological responses (mortality and sex ratio) of S. harmandi reared on M. alternatus improved over multiple generations. S. harmandi females of the 12th generation on the target host showed better performance, i.e., shorter time for searching and handling, higher oviposition preference, and, subsequently, lower offspring mortality and proportion of male emergence on the host than those from the base stock. Our work demonstrated that these traits in S. harmandi were influenced by the integration of cultured generations and host quality, which implies that the potential effectiveness of S. harmandi as a biological control agent can be further improved.