Temperature-driven embryonic diapause in the polyembryonic endoparasitoid Macrocentrus cingulum (Hymenoptera:...

Parasitoids are vital biological control agents in sustainable pest management. Their diapause can be exploited to extend storage duration and synchronize adult emergence, thereby facilitating mass rearing and field release programs. However, key diapause traits remain poorly understood in many larval endoparasitoids, particularly polyembryonic species such as Macrocentrus cingulum Brischke, an important natural enemy of the Asian corn borer, Ostrinia furnacalis (Guenée).

Low temperature was the dominant and sufficient cue for diapause induction in M. cingulum, independent of host diapause status. All parasitoids entered diapause at 17 °C, whereas no diapause occurred at 26 °C under 10 h light:14 h dark, even when developing within diapausing hosts. During diapause, development was arrested at the blastula stage, and embryos exhibited abnormal morphology and arrested cell proliferation for up to 46 days. The diapause-sensitive period extended from embryonic primordium formation to darkly stained cell aggregation and required at least 25 days of induction. Diapause could be terminated effectively either spontaneously or artificially. Although a transient reduction in fitness was observed immediately following diapause termination, female performance remained intact, and fitness was fully restored in the subsequent generation.

Low temperature alone is sufficient to induce host-independent blastula-stage embryonic diapause in M. cingulum. These findings provide a practical framework for improving parasitoid storage and deployment in biological control programs and establish a foundation for investigating the mechanisms underlying embryonic diapause in parasitoids. © 2026 Society of Chemical Industry.