AbstractTwo new developmental pathways were found in Scelio bipartitus parasitising diapause eggs of Gastrimargus musicus in a temperate region; overwintering as pharate adults within the host egg to emerge in spring; and overwintering as larvae with development to the adult stage and emergence in late spring. A third pathway, nondiapause development to the adult stage in late summer and emergence in autumn was observed for the first time in a temperate region. Parasitism rates ranged from 4.3–11.7% in the first year of an outbreak to 61.5–87.5% in the second (final) year. In Queensland, G. musicus occasionally overwinters as nymphs and oviposits in spring. Overwintering by S. bipartitus as pharate adults is a possible adaptation to this host developmental pathway.