Termite queens adjust egg size according to colony development

The trade-off between egg size and number is one of the most discussed concepts of the life-history theory. However, little is known about social factors influencing this trade-off in eusocial insects, where queens and workers share energy investment in the brood. During the colony-founding stage, the founder queen produces eggs and also rears the first-brood offspring independently in the absence of workers. The larger colonies have more labor force for brood care, as workers feed larvae until independence, whereas queens need to increase oviposition rates as the colony develops. Thus, social factors, especially the number of workers, should influence the trade-off between egg size and number. The adaptive investment hypothesis predicts that queens allocate more resources to individual eggs in the colony-founding stage and reduce egg size with increasing worker number. We showed that queens produce smaller eggs in larger colonies in the termite Reticulitermes speratus. We found a highly significant negative correlation between egg-laying order and egg size in the colony-founding stage. The first-brood eggs in earlier laying order exhibited shorter hatching periods and developed into larger larvae. Production of remarkably large eggs in the early founding stage likely has great adaptive significance, as the timing of the appearance of the first-brood worker is critical to the survivorship of incipient colonies. Copyright 2010, Oxford University Press.