Reproductive traits of the egg parasitoid Aprostocetus fukutai, a promising biological control agent for invasive citrus longhorned beetle Anoplophora chinensis

Aprostocetus fukutai (Miwa & Sonan) (Hymenoptera: Eulophidae) is the only known egg parasitoid of the citrus longhorned beetle Anoplophora chinensis Forster (Coleoptera: Cerambycidae), a high-risk invasive pest of hardwood trees. Native to East Asia, A. fukutai has been accidentally introduced in northern Italy, where it has 1–2 generations per year, overwinters as diapausing mature larvae within host eggs, and adults emerge in early summer in synchrony with the egg deposition of its host. As part of the efforts to develop a biological control program using this specialist parasitoid, this study investigated some of its key reproductive traits, including egg maturation dynamics, host egg age preference, clutch size, and lifetime fecundity under quarantine laboratory conditions. Newly emerged adult females after winter diapause had a substantial proportion (43.7%) of their lifetime complement of mature eggs and matured additional eggs rapidly, reaching a peak 4–8 days post-emergence. The parasitoid preferred to attack 1–3 day old over 4–7 or 7–10 day old host eggs. Adults of the first (overwintering) generation were more fecund than those of the second (summer) generation. Females of the first and second generations parasitized 3.6 and 2.8 hosts, produced 11.2 and 9.6 offspring per parasitized host for a total of 37.5 and 24.7 offspring with sex ratio of 85.3 and 82.8% females over their lifetime, respectively. These results provide novel information that may help improve protocols for future rearing, study, or field-release of this parasitoid against A. chinensis.