Worker mortality and the evolution of castes in the social wasp polistes exclamans

Workers of the primitively social wasp, Polistes exclamans, had very short average lifespans, averaging 14 days (S.D.=11, N=497) in 1977, 17 days (S.D.=14, N=503) in 1978 and 14 days (S.D.=10, N=222) in 1979; the oldest worker observed on a natural colony was 102 days old. Colony of origin explained more of the variance in worker longevity than did any other variable. Worker longevity decreased over the season, accompanied by an increase in larval development times and an increase in colony failure rates. In 1978 workers emerging in the presence of greater numbers of other workers lived longer which indicates that they may have performed risky tasks less often when many other females were present. Compared to 1977 and 1979, 1978 was characterized by greater numbers of workers per colony, shorter larva development times, longer average lifespans for workers, much higher probabilities of nest survival and greater average production of reproductives per colony.