Foundress Mortality after Worker Emergence in Social Wasps (Polistes)


Biology Department, Rice University, P.O. Box 1892, Houston, Texas 77251, U.S.A.


Worker emergence is a watershed in the development of a social insect colony because after workers emerge subordinate foundresses are less critical to the survival of the colony, and may be simply a threat to the egg laying monopoly of the queen. A widely-held view is that after worker emergence the queen either kills or chases off subordinate foundresses in Polistes, as is the case in many ants. Our examination of changes in subordinate behavior and mortality after worker emergence reveals a more complex picture. Though foundress mortality increased significantly after worker emergence in 5 of 7 populations of Polistes (6 different species), this did not always result from increased queen or worker aggression toward subordinates. Senescence may also play an important role in subordinate foundress mortality. The two species in which subordinate mortality did not increase significantly after worker emergence were characterized by high rates of colony failure due to loss of all workers. This may indicate that subordinates remain in the colony after worker emergence in species where their continued presence is important to the success of the colony.