Oophagy and Egg Replacement in Artificially Induced Colonies of a Basically Solitary Bee, Ceratina (Ceratinidia) okinawana (Hymenoptera, Anthophoridae, Xylocopinae), with a Comparison of Social Behavior among Ceratina, Xylocopa and the Halictine Bees

1) In-nest behavior of Ceratina differs from that of Xylocopa in : 1-Cell wall and the surface of the partition are not lined with secretion. 2-Pollen loaf is formed on the cell floor without changing its position, and additional nectar is also admixed after the end of daily foraging. 3-Aggressiveness is virtually absent between the partner females. 4-Oophagy usually does not appear soon after oviposition. 2) The number of eggs that escape oophagy does not differ significantly between kin and non-kin colonies, whereas the percentage of oophagy and egg replacement is quite different between C. okinawana and C. flavipes+C. japonica. 3) The sequence of oophagy and egg replacement varies markedly from case to case, suggesting an unstable power relation between partner females. 4) The sex of each egg laid can be estimated from the oviposition behavior. 5) A tentative plan to clarify the relation between kin selection theory and egg replacement is presented, together with difficulties involved. 6) Social degeneration of C. japonica and C. flavipes during their evolutionary changes to temperate species is assumed. 7) Social behavior of Ceratina is comapred with those of Xylocopa and the social halictine bees, particularly of Lasioglossum zephyrum.