Diapause and Non-Delayed Eusociality in a Univoltine and Basically Solitary Bee, Ceratina japonica (Hymenoptera, Anthophoridae) : I. Diapause Termination by Cooling and Application of Juvenile Hormone Analog

Ceratina japonica is a univoltine and basically solitary bee, but it can occasionally form semisocial or delayed eusocial colonies. For this species the artificial termination of reproductive diapause within the active season seems necessary to induce the non-delayed eusociality, the life mode common to all temperate social insects. In this study the possibility of diapause termination was tested by two standard methods, cooling pre-hibernating adult females (also for an allied species, C. flavipes) and topical application of juvenile hormone analog (JHA) to prepupae and pupae. The rate of termination rises over 50% by cooling at 5-8℃ for 3-4 months. However, this method is too time-consuming to match with the univoltine life cycle of C. japonica and JHA application is the only known possibility to induce non-delayed eusociality in this species, in spite of its low rate of diapause termination, only 35% by our procedure.